] ■ f L I "'^<§®5W? 3SSBM ate S^Twa^OBEaj^ rCSS^^^Wl HM3P^ 2Z^E$LXS1@ ^ , <'^lC ? ' C ;CC Ipc^aEsg CTSC j XCfT^^LC ; j <&• o^>3aO \p£M!S0 \8 ) and below it: In explaining of which, Iihall demonftrate the Caule of the Failure thereof, wherein note, L. The Pier that was rebuilt, and now ftanding on the Ruins of a former Arch, as before-mentioned. M. Part of the Underwork of the fecond Pier of the Foot-way, failed and carried oft by the Floods. N. Shews a Diagonal opening quite acrofs the third Arch, caufed by the fecond Pier having funk into the Bed of the River Weftward, and the third Pier Eaftward. O. What now remains of the .fifth Pier. P P. The two Piers of the Foot-way that have funk the moft into the Bed of the River. Bafs of the Effigy. R. Shews how the Current is now difedled by the Bafs of the Effigy, the Confequence of which fliall be hereafter explained. S S. Shews the Soundings of the River at High-water, taken in a dire5 \ 20,6 ; 1 & 6 17. 71 n-5 IS .<1 17*9 1A *s 1C , <7 ‘13 s ¥ \ {- ■■ V • - 9 <• 1 jjs=---^- -- 1^- ■' ~-4 r',T^ i t I 4 4 i ff f * ■• i .* M i A V * i / \ I S * * O* v 4 r <•• . * • s* »> ^ ^ ; .ii > V 1 « ; V r \ \ % i % / * * %■ $ \ / « / <•, • • •' *•** • - \Av «? -»»**»**.• «-C I f \A / r t \ i \ i \♦ * I I V i 0 O j ; ^ s t I \ < * »( 37 ) Shaft. Fig. 2. (by an Inch to a Foot) is the Plan of the Ram; and Fig. 3. is the Upright of it with the Staple, that the Tongs take hold of. This Ram is only four hundred and a half, which, may be fully fufficient for thefe or the like ordinary Occafions; and for more weighty Work, you may on the fame Principles proportion the Size of the Ram to the Size of the Engine which you think you will want. EXPLANATION of Plate XII. Scale 8 Feet 1 Inch. Fig. 1. is the Plan of the Timber of the Floor of the Pump-Engine, with the Situation of the 8 Pumps, and Centre or Socket of Brafs, on which the main Body plays. Fig. 2. Section of the Engine, wherein note, that a. is the bottom of the Pool; b. Low-water Mark; c. is the Inclofure of Piles and Boards that keep up the Banks of the Pool; d. High-water Mark; e. open Gutters, that convey the Wster from the Pumps over the Dike; f. both in Fig. 1. and Fig. 2. and D. in Plate VII. are the Trunks that either carry off the interior, or let in the exterior Water occafionally at Low-water Mark, to which there were Sluices fixed in the middle Stage of the Dike, that were wound up and down by a Jack. From my firft forming an Idea of the Inclofure, my Mind was conftantly opprefied with the dread of its burfting in upon the Men, when they were at Work in the Pit as before-mentioned; from which intolerable Anxiety, I was relieved by contriving thefe Trunks.. I cannot tell whether Colonel Beiidor uled any fuch Thing, becaufe as I before obferved, I was ignorant of the Language he wrote;in; but I am well allured, and you will hereafter find, that they were of infinite Service to us. The other Parts of this Engine'are obvious, as indeed, there is fcarceiy any good Millwright but what may comprehend and execute the whole Con-flrublion of it. Having now to the utmoll of my Power fully confidered every Thing relative to this Work, I fat down, and by theAffifiance of my Biother made an Eflimate of the Expence, fuppofing the Balluf-C 38 5 Balluftrade to be made of Fire-florie; and we found it amounted to twenty thoufand Pounds, and I promifed that I would not exceed twenty thoufand five hundred, for we allowed the five hundred for Incidents; and I computed, that within, or about the Space of two Years, from the Day upon which I fhould flop up the old Bridge, that a fafe new Road might be made over the new Bridge for Carriages; and upon thefe Calculations and on mature Deliberation, I made the following Declaration, not only to the Overfeers with whom I treated, but alfo, promifed to the Lords Juftices, to the Committee of the Houfe of Commons, and to the Public in feveral Papers to this Effedt. 1 ft. That I would build them a Bridge that fhould fiand as long as a little adjacent Mountain called *Sugai loaf-hill. 2d. That the Expence fhould not exceed 20500/. 3d. That I would have a Road opened for Carriages over it, within or about two Years from the Day of my flopping up the old Bridge as above-mentioned; but I did not any otherways bind myfelf to the Performance of any of thofe three Articles, yet not-with(landing, I looked on myfelf to be as much bound to the Performance of them, as though I had engaged for them under my Hand and Seal, and flaked any little Reputation I had acquired, faithfully and effedfually to perform them to the utmoft of my Power. CHAP. VI. SECT. I. Of demolijhing the old Bridge. WE began on January 19th, 1753, to flop up and demolifh the Bridge, and1 take down the Equeftrian Statue of King George 1. which had been put up in 1722. February 19th, we drove the firft Pile of the Coffer-dam. In pulling down the Bridge, we began at the South, and took in the largell: half of it in order to open and deepen that Side, to let the whole Current run there. In doing of this, I found it neceflary to make a temporary Dam, to turn the River to the North, in order to lengthen the Time of Ebb^ and clear away the old Ruins, &c. After( 39 ) After this Dam was made, we were going on very fuccefsfully till the 28th of April, when there came down a pretty ftrong Land-flood, which obliged me to take the Men off that Part of the Work. I then flood on. the northerly Part of the Bridge, dreading the Fate of our poor little Dam, when I efpied the Water within Side of it grow very black, the caufe of which I well knew to be the blue Clay burfting out, and I hurried down to it in order to fee if there was any Poflibility to fave it; but the very Moment I had got on the top of it, I found the whole rife up under me, and had not above a fecqnd of Time to fave my Life; for the Floor that was on the top of it turned immediately down, and the Points of the Piles rofe up, and notwithstanding the Activity of the Men, great Part of it was carried down the River; but this Frischt was of much ufe to me, for as the caufe was the Floods get-ting in under the Clay, I was ever after on my guard by making our great Dam in fuch a Manner, as might refill the Force of any Land-food or Torrent. May 3 ?, the laft of the Piles of the Coffer-dam was drove, and 'June 4th, we began to fill the Clay into it, and the fame Day having taken up all we could of the Foundations, we began to deepen it by drudging. SECT. II. Defcription of the Foundations. f p A H E Foundations of this Bridge, or rather the Piers‘of it as $|_ before mentioned, were built after this Manner. They made Frames of Oak of 9 or \0 Inches Scantling, the exadl Shape of the Pier, with rough two Inch Planks of Oak Dove-tailed a- * / O crofs it, in every three or four Fe-et and pinned to the Frame, and on thefe Planks they flretched other Planks Length-ways but not fo thick. Thefe Frames fo made, they dragged to their Birth, and let them reft upon the natural Surface of the Bed of the River. The Piers being extremely grofs, increaled the Rapidity of the Water between them, and the 'Bed of the River (as you have already( 40 > ready feen) being fharp Gravel, the Floods fwept it down as before-mentioned, and indeed, the only Thing furprizing is, that it flood fo long. Now I am come to one particular Circumflance, which I recommend to your ferious Attention, as I fhall hereafter endeavour to draw fome ufeful Inferences from it. After we had got fome of thefe Frames taken up, particularly the third, we found under the inner Part of it, a fmooth Floor of clean fharp Gravel, hard and firm under our Feet; but when we thought to go on with filling the Floats with it,/to‘carry it away, as we had done in the Bed of the River between the Piers, we found it very hard, and as the Shovel could not move it we tried the Pick; but when we had got a little further into it, the Pick made little Impreffion upon it, and when we got further into it, we found that we had no other Way to break it, but by undermining it, and then break it off in Pieces with the largefl Sledge we had. The middle of it was an a<5hial Petrification of about a Foot thick, but not fo hard in the bottom as in the top. Some of the Piers were much more petrified than others, and particularly this, as being better guarded by the Bafe of the Effigy, and having imbibed the petrifying Qualities that foaked from it. The Grit or Grain of it greatly refembled that of a Mill-flone; but the Colour was juft the fame with the Bed of Gravel it lay upon. Where the Gravel partook of Mud, the Pier that lay on it was not near fo hard, and thofe Piers did not petrify at all that lay on Beds that were not gravelly. 1 E C T. III. Breaft-worl for the North Abutment, Jhewing the Method of beeping up a Bank of loofe made Ground upwards of 30 Feet high, on only ten Feet Projection. WE began June 8th, to fink for the Abutment, which was a Piece of Work I was afraid would be attended with very great danger, becaufe I had a very great Depth to fink, and very littlei \ ' I % \ / i( 41 ) little Room to link upon, without depriving the Public of the ufe of the Carriage Way. » EXPLANATION of Plate XIII. Scale 5 Feet 1 Inch. In this Plate, Fig. 1. reprefents the Method I took to keep up the Bread: of the Bank, wherein note, A. Pavement. B. High-water Mark, which is 9 Feet 4 Inches from the fame. C. Low-water Mark = 10 Feet. D. Bottom of the Pit 11 Feet, that is = 31 Feet 4 Inches. E. Is the whole Projedtion of the Breaft-work, which is 10 Feet, and that I divided into 4 equal Parts, allowing 2\ Feet to each Stage. Having Brained a Line at right Angles to the intended Bridge, and 10 Feet from the back of the Abutment, we funk about three Feet, and then drove in a range of 4 Inch Piles clofe to the Bank; then with paving Hammers we chipped off fo much more of the Bank as jud: barely admitted the ilieeting to Hide down between the Bank and the Piles; and when we had funk 8 Feet in this Manner, we made our firft fet off Feet, and proceeded in the fame Manner as you may perceive by the Draft; but after we had got down to the third Stage, we always kept Braces againft the Breaft-piles, which we removed down according as we funk; and notwithftanding the almoft conftant running of Carriage?, and the Banks being all made Ground, there- did not fall one Handful of it in upon us. When we had got down to about the third Stage, or a little under Low-water Mark, we had all above us compofed of various forts of made Ground; but from and about that level we found the Ground begin to incline to fine fundy blue Clay, fometimes mixed with Shells, and fometimes with Leaves, which v/e took to be Bay-leaves, all of which, we concluded had in former Times been left there by the Sea and River, becaufe we got in it a imall Tree almoft rotten, with fome of the Brandies ftill upon it; at the Butt it was about 4 Inches Diameter, but no one could tell with Certainty what fort of Wood it was of; from all which, I concluded that I did not raife any Irefh or natural Earth. It is not my Intentions to give a minute Detail of all the various Circumftances relative to our Proceedings, for that, perhaps, G would( 42 y would be more tirefome than inftruclive; and therefore, I only give a concifc Abftradt of a few Particulars taken from our Diary, in order to convey a juft Idea of the whole of that Work; but having made one very extraordinary Difcovery in this Place, which alarmed every Man in the Work, and greatly furprized a vaft Number of Gentlemen that law and examined it, I fhall relate the principal Parts of it in the next Chapter, and referve the Explanation of Fig. a. for a more convenient Opportunity. CHAP. VIL An extraordinary Difcovery at eleven Feet leneatb Low-water Mark. If J" A VING got fome Part of the North End of the Pit funk JL JL down to about ten Feet beneath Low-water Mark, and quite free from Water, except fome fmall Quantity that foaked from the Bed of the River, which was then about the farfle Space above us, and that we conveyed into the S. E. Corner for the Screw-pump; the Men that were finking for the Land Abutment perceived one Spot in the Ground that grew very wet, but did not much regard it; but in finking the next Spade which was about a Foot deeper, when they had laid open that wet Spot, we were all greatly alarmed by the very ftrong boiling up of the Water juft in that Place. I lent immediately for my Book of Borings, and found that wet Spot was Boring N°. 28. 1 immediately called for one of the Boring-pipes, and had it drove down to the Rock, and the top of it was 3 ' Feet above that Floor, on driving of which the boiling entirely flopped. This gave us fome Spirits, and the Men went on with their finking that Floor, but at this Time the Tide was at Ebb; but when the next Tide rofe to about fix Feet, it began to boil over the Head of the Pile, and increafed in force as the Tide rofe, and fo greatly wet the Work that we found it ad-vifable to plug up the Pipe, and fo we continued to hurry on the Work, without taking any further notice of the boiling, except looking on our Jetteau as a Matter of Curiofitjj which during the Time( 43 ) Time of High-water and after it, when we would pull out the Plug, would play upwards of a Foot above the Head of the Pipe with great force. The Rev. Dodtor Hudfon, who was a very curious and condant Obferver of our Proceedings, came to the Work the next Morning, and I brought him with feveral other Gentlemen to the Work, to fee our curious Jetteau: He called for a Glafs, and they all tailed, fmelled and attentively obferved its Colour. They then dropped a Piece of Silver into the Glafs, which was foon turned to a dark yellowifh Colour; and at Length, they all concluded that it was a mineral Spa, and advifed me to fend directly for Dodtor Rutty, for whom 1 went myfelf, and he cheerfully came with me, the Gentlemen waiting for us: He tried all the before-mentioned Experiments over again, and acknowledged, that it feemed very like the Water of Swaddling-bar; but concluded, that any Sea-water that partook of putrid Water, running from a foul Sewer, might have the fame Effedls that had, and he dehred me to fend fume of it home with him, which I accordingly did. This Adair engroded my whole Attention, and put me upon making the following Experiment. See Plate 4. Boring N°. 28, and fee thatN°. transferred to Plate 5. which is the Boring mentioned above. I then had two other fimilar Pipes drove at ten Feet didance from it to the Eall and Wed, viz\ 29 and 30, and 1 bored them in the like Manner at Low-water, and as the Tide came in, l found the Water rife in all the three Pipes exadlly alike, and at or loon alter High-water, they all played together when we took out the Plugs, near a Foot above the Heads of the Pipes, which were all on a level; and as the Tide fell, they abated in their Force, but never funk lower than the tops of the Pipes, which as 1 L id above, was 3^ Fee$ higher than the bottom of the Pit, and coiBqucntlv 7! Feet under Low-water Mark. The next Morning Doctor Rutty, and DocSr Hud-fin came to the Work, where they met the Gentlemen that were there the Day before, and he, Doctor Rutty, then allured us, that it was no Species of Spa-water, but lie believed, a large Body of fubterraneous Water, that ran along on the Surface of the Rock, and communi- G 2 catcd( 44 > catecl with the Sea-water, and partook alfo, of the foul Waters of the Bed of the River and the Sewers. He then produced us as much Salt as would cover a Shilling, which he faid, he had ex-tradled from one Pint of that Water, which was not near fo much as a Pint of Sea Water would produce;, and concluded with giving me this friendly and ufeful Caution, u take great Care that you do not let that Water break up upon you, for if you do, you will never conquer it.” This Opinion of Dodtor Rutty s coroborating with my own, it was inftantly circulated among all the Men in the Work. They all unanimoufiy joined in exerting themfelves to the utmoft of their Abilities; for that Water alone, was not the Caufe of our Anxiety, as we were at that Time thirty-one Feet deep under the Surface of the Pavement, which was within ten Feet of being perpendicular over’us, and all being made Ground, with a fine Sea Tandy bottom, which notwithflanding all the Precautions we had taken in finking and fhoring up our Bread-work, we well knew, that if the fmalled Quantity of Water fhould then get into the Pit, it would mod afiuredly lap and foften that fine Sand, which together with the continual fhaking of the Ground by the Carriages, would render it impoffible for us to prevent its burding in upon us, and in all Probability pull in the Corner-houfe along with it. Hereupon we agreed, that it would be bell and fafeft for us to defid from finking any deeper, though that was no final! Difap-pointment to us, as we then had thoughts of going down to, or very near the Rock, nor otherwife had we any Difficulty to encounter with in accomplifiiing it; for the Floor we were then levelling and clearing out next to the Bank, was perfectly free from. Water, except what little Iprang up with the three Pipes; but remembering Dodlor Rutty's Caution, which I knew to be well founded, I proceeded with all poffible Expedition to make the Maions fecure the bottom, of the Bread-work. September 23, The Mafons began to lay the thorough Foundation, but particularly to fecure the bottom of the Bread-work, which extended about 15 Feet from the Bank, and in the mean Time the Labourers were clearing out and levelling about 20 Feet more,( 45 ) mare, which being juft accompliflied they were hurrying in Stones to be ready for the Mafons, except one Man, who was left to throw out and level fome fmall Matter which they left undone; but all the alarms and frights we had met with, were nothing to a frefh Difcovery which that Man firfh obferved; the Floor (which was dean, fmooth and dry) opening, I was inftantly called, and when I got on the Spot, could clearly perceive the Ground fwelling up and opening, (See N°. 31, in Plate V.) and it foon. extended to about the Length of 10 Feet, turning rather foutherly at the Weft End, and the Crack or Opening was about three or four Inches wide in the Middle. The Tide was then about ten Feet high, and in the Middle of the Crack we found the Water beginning to fpring; up, which gently increafed to about a Foot Diameter, and fprang pretty faft. I called fo-r another Pipe of the fame Length, and had it drove down in the Centre of the Ebullition, or Boiling up, till it came to the Rock, and having bored and cleared it as before, which eafed and gave it vent, we found the Water rife up, and in Fa£t the very lame fort as came up in the three former Pipes, and to the fame level, altho’ chis Pipe was 1 7 Feet to the South of them; and we plugging up this Pipe alfo, the Men did all in their Power to get in Stones and Mortar ready for the Mafons, and in the mean Time the Water that fprang up through the Crack, rofe 18 Inches deep in the lower Part of the Pit; but providentially we then had the Mafonry built above fix Feet high againft the Bank; but wh^n the Ebb came it defifted, and we foon got out the Water, and laid the largeft and flatted: of our Stones upon the Crack, fpread-ing fome Litter under them, and before the next Tide had that Part of the Foundation almoft -as high as the other; for, from the Time of our getting the Bridge taken down to Pligh-water, we wrought both Night and Day, without one Minute’s Intermiflion,, as we had two fets of all forts of Men that relieved one another alternatelyxevery eight Hours, not excepting even Sundays, when our urgent Occaflons required it: Yet, notwithftanding we had luckily conquered that fubterraneous Water at fo critical a Time, it never failed every Tide, whilft we wrought in that Pit to contribute greatly to the increafe of the Pump-mens Labour; but as we( 46 ) we wrought with unremitted Perfeverance and great Expedition, we moil fortunately prevented its burfting up upon us. And of this I am well allured, that if we had not that lnftant loaded that opening of the Ground, the fubterraneous Water would certainly have broke in upon us, and if it had, there could have been no Kind of Poftibility of ever building a fubftantial Bridge in that Place, confidering the Condition that every Thing was then in, and fo many thoufand Pounds worth of Labour and Materials would have been totally loft, and our then hopeful Projedts entirely at an End, as Dodlor Rutty had told us. CHAP. VIII. A Continuation of the AbfraR of our Diary, and laying the Foundations of the North Piery 21 Feet beneath the njual High-water Mark. WrE made the firft Trial of our Coffer-dam on June 27th, and it kept out 3,Feet 6 Inches of that Tide, July 3d, we fcrewed down the Sluices when it was High-water, and kept them down till half Ebb, in which Time the Water in the Dam fell three Inches, and thus we tried and proved its Stanchnefs feveral Times, both backward and forward; but the South Eaft Corner of it that flood on the great Depth of Stones that had been carried down by the Floods into that deep Pool, was like a French Drain (as before-mentioned) which we began to defpair of ever getting made even tolerably ftanch. July 7th7 we fcrewed down the Sluices at low Water, and before high Flood difeovered that the Tide Water had wrought its Wav in under that South Eaft Corner through the Stones and Rubbiih of the old Bridge, and began to fpring up about 20 Feet within our Dam after a very furious Manner; on the firft Appearance of which, I ordered the Sluices to be fcrewed up and let the Tide in, by which we drowned the Springing, which did us very little harm; and at low Water I fet all the Drudge and Water-men to that Corner, both without and within, and in Short, we took out and removed( 47 ) moved from that Corner every Stone that was in our Power, and filled the Vacancies with Clay, &c. Aug. 3d, The Sluices were fcrewed down at low Water, and when there was nine Feet Flood without, the Water had rofe'only thirteen Inches within. 5th, After an exceeding heavy Rain there came down a fudden? rapid Flood, and tore away many of the Ships and Lighters from the Quay, fnapping their Moorings as a burned Pack-thread, and did them great Damage, but we were prepared for it, and kept open our Sluices, fo that the Water then rofe as fad: within as; it did without; but it did us no other damage than delay us a little, and wafh away fome of our Clay; and after all this, the next Day we: proved the Dam again, and during the whole Tide, the Water within rofe only four Inches. EXPLANATION of Fig. 2. in faid Plate 13. Wherein note, F. The Rock. G. Strata of fine fandy Loam,, which is in this Place, three Feet fix Inches thick from the Rocky on which the rough Stone Work begins. H. The lad: Courfe of the rough Stone Work, which is laid with very large Stones carefully bedded and wrought clofe in their Joints, to guard the thorough Foundation between the Piers from ever being difplaced, or torn; up by the Water, which is about four Feet deep at low Water. i. i. i. Fig. 3. Are the Ends of three Four-inch Planks that dretch quite a-crofs the Foundation, and on which the Sills of the Centres-k. red. 1 When you are doing the like Work, obferve that between thefe running Planks and Sills, to lodge in Wedges of about H Feet long, leaving about one Foot of them out, and when you come to drike your Centres, defcribe or mark them deep, that you may know how far you bring each of them out, by driking each Wedge on each Side, and by that Means you will work out the Wedges by Rotation, till you have eafed every one of them about one Inch, and then proceed after the fame Manner, till you have eafed them all about another Inch, and fo proceed till you have got them all out; after which you may go on with taking them? down after the ufual Manner. And this I recommend as a much fafex( 4« ) fafer and a more pra&icable Method, than Screw Wedges, which fome have very warmly recommended. September 28th, at 3 o’Clock in the Morning we fet the firft Cut-ftone of the Land Abutment, without any Parade, which Time would not admit of. November 1 ft, we compleatly finifhed the North Pier, fpringing high, and cut the fix Inch dovetail Piles, that cafed the thorough Foundation juft at the Surface of it, half through, fo as we might eaftly break them off there when we pleafed. 6th, We took up the ftrait Beams that went a-crofs the Pit, in order to let the Carpenters put up the Centres of the North Arch. E X P LANATION of Plate XIV. Scale 5 Feet 1 Inch. Fig. rft, Reprefents the Plan of the Foundation of the Weft end of the North Pier, with the rough Mafonry wrought up about the Piles, and -inclofed with a Row of fix Inch dove-tailed Piles, fuch as you will fee in Plate XV. Fig. 6. which were half cut off at the Surface of the thorough Foundation, and then broke off, leaving the lower Part to cafe and guard that Foundation. The other two Rows of fquare Piles and their Sheeting, hold the Clay, which together make the inner Coffer or Pit. Fig. 2. Section of the fame, and the Weft End of the Pier. Wherein note, A. Rock. B. The Bottom of the rough Mafonry. C. Low-water Mark, which is eleven Feet from B. EXPLANATION of Plate XV. Scale 5 Feet to 1 Inch. Wherein note, Fig. 1. Shews the Bond of the Cut-ftone in the bottom or firft chained Courfe, of the Pier, with a Part of the rough" Stone Foundation, covered over with large thick Stones Home to the dovetailed Piles, the Surface of which is four Feet fix Inches beneath Low-water Mark. Fig. 2 and 3. fliew the Bond of the Cut-ftone in the other two Chain Courfes. The Chain of the firft Courfe was near three Inches Square, and the Chains of the other two about 2 Inches Square, and all funk their full Depth, andMffi i mm piffi 'Ld' AJM- » M ij 11 j ■ ynVl mvi ' na kfl \ \ I \ \ v / m \i / /' / ML l Cn£ mZ £ /I i ggil ru~ir P Km! RSj km n B) E9 v - > A/ ) p % '• » ^ • Jf i «v ♦- * *■ «•€***-* *-«vM' * • mv ****** ' •/ • t sr V v <*V *Av, '. \ I f * \ * * / / % t ■v * / %( 49 ) and run with Lead. Fig. 4 and 5. are two different Methods of making dovetailed Piles. Fig. 6. is the Method that Belidor feems to have made ufe of, and I followed the fame; but in my Opinion, Fig. 4. is both the bed; and cheapeft, for many obvious Reafons. The Method we took in laying the Foundation, was this; after we had drove the Oak Piles down to the Rock, which you faw in the laft Plate, we fpread a plentiful Coat of Roach-lime and (harp Gravel over the Ground, and laid a Courfe of large flat Stones, and filled and hearted them in clofe about the Pile for about a Foot high; then we covered that Courfe with another plentiful Coat of the dry Grout (i. e the Roach-lime and fharp Gravel) and the next Courfe and all the red: was laid with Mortar after the ufual Manner, only with this Difference, that every Stone fwam in Mortar, and each Courfe was grouted as above; and fo we went on till we came to the level for the Caps that were laid over each row of Piles, and then wrought up and levelled them, on which we laid three Beams firetching the whole Length of the Pier from Sterling to Sterling, and filled up about them with the Mafonry; but the thorough Foundation that lay under the Arches, was laid and fecurely bedded, and many of the Stones were rather pitched upon their Ends and wrought clofe together, fo that there is a fubftantial Stone Floor for the Bed of the River between the Piers, on which we fpread a Courfe or Stratum of about a Foot thick offharp coarfe Gravel mixed with new and old Lime-rubbifh, and we covered that with a plentiful Bed of fuch coarfe gravelly Stuff as we could colledl within the Dams, which together, made on an Average about Feet thick; my reafon for laying this covering on the Surface of the Foundation, was principally to preferve the green Mortar that lay on that Surface, from being waflied away before it would get proper Time to cement; and as I had 4 ‘ Feet from that Surface 16 the Low-water Mark, I concluded, that for the p’-efent Time two Feet deep would anfvver the Purpofes of Navigation, and we finiftied all the reft of that thorough Foundation in like Manner, except the South Arch. I am fenfible-there was no fort of N X ✓ t s l v l\ \ t / * C 5r ) all which Time, our Sluices being open, we fuffered little or no Damage, except lofs of Time, and the diffurbing our Stages, Utenfils, &c. for all the Water being at the fame level within and without, it was perfectly ft ill and quiet within the Dam. From the 4th of December 1753, to the 23d of February 1 the Floods continued extremely high, and often to 13 Feet at high Water, which greatly retarded our Work; but otherwife, did not do us any confiderable damage: However, we were now enabled to put the rough Mafons to get ready the Foundation of the fe-cond northerly Pier, which we executed juft like the former; and within the Space of four Nights and Days, we had it ready for the Stone-cutters, that is, on the 27th, the Stone-cutters laid the firft cut Stone of the 2d northerly Pier. March 19th, We began to drive the firft of the Piles of the Coffer-dam for the 2d principal Operation on the South Side. See Plate XVIII. Scale 40 Feet 1 Inch, 29th, Second northerly Pier fpringing high. 30th, The Stone-cutters began to lay the firft Courfe of the ad northerly Arch. April 8th, The Coal-gabbards were flopped for the firft Time, and milled three Tides, when we cleared a Way for them under the northerly Arch. 22d, They began to pull down the Excife-office; by the delays given to us on that Account, we loft eight Days of the fineft Weather we had had for a Year paft. 25th, Part of the Cuftom-houfe Quay fell, by which we difvo-vered another old Quay-wall, 6 Feet within that. May 23d, Both the North Arches open and free for the Coal Gabbards. 25th, There came down a fudden rapid Flood from the Mountains, which wafhed away a great deal of the Clay, which we were putting in the Coffer-dam. June 5th, From the 25th of lafl Month to this Day, we had conftant Land-floods; the Ebbs feldom fell under 3 ‘ or 4 Feet. Thefe Floods defiroyed a vaft deal of the Clay, but with grea-: H 2 Difficulty( 52 ) Difficulty we got the Current turned entirely into the North Channel, to its full Depth. 14th and 15th, The Land-floods at Low-water were from 8 to 9 Feet. 25th, This and former Days we had great Labour in taking up the Ridge of loofe Stones, which lay in a direct Line quite a-crofs the River below Bridge, as before-mentioned; but dear bought Experience had taught us to fpare neither Time nor Coft to get thofe dreadful Pefts removed from under the Dike. July 27th, Thefe fix Days we had exceeding rapid Mountain Floods; high Warer generally about 11 Feet. Auguft 4th, We finiflied the rough Stone Foundation of the South Pier of the middle Arch. 5th, The Stone-cutters began to fet the fame Pier. 1 2th, In drudging for the South-eaft corner of the Dam, we met with very large Cakes of the petrified Sand, that the Floods had carried down into the deep Water, which they were forced to break to fmaller Pieces, by driving well-fhod Piles into them. 28th, We flopped all the Pumps, as we had no further Occafion for them. From the 20th to the 28 th of September, we were obliged to flop the Carriages, from going along EJJ'ex-quay, on account of our finking for the South Abutment, in doing which, we raifed Part of the Foundation of Newmans "Tower, which had been very judicioufly laid on the lolid Rock, and we were alfo obliged to quarry in fome Places two or three Feet deep of the Rock, to bring it to a proper level, and omitted two Courfes of the Cut-flone of that Abutment, as the third of the projecting Courfes were laid upon the folid Rock. OEloler 7 th, The Abutment finiflied, fpringing high, and the lame Day we began to lay the Foundation of the South-quay Walls. CHAP.( S3 ) CHAP. X. The proper Method of building Quay lVails ^ and a Continuation of the AbfiraU of our Diary. T SHOULD think myfelfvery reprehenfible, did I forbear to ^ difcover the true Proportion of Quay tValls, which I was taught by .an eminent and worthy Gentleman, Major Marcell\ but previous to the Proportions, there are other Things to be confidered, the principal of which is, the Nature of the Ground on which it is to be built, and to be fure, if it be not Prong enough, that you make it fo by. piling, and that the Foundation of the Wall be laid of a fufficient Depth, the front Courfe of large and long Headers, that will admit of making a good fet-off; all which being duly confidered, you are then to calculate how far that Foundation is to project. The Major’s rule is this, 44 That the out-fide of a Quay Wall, ought to batter one fixth Part of the Height of it.” And left you fhould not clearly underftand this moft excellent rule, I fhall perhaps make it the more intelligible, by giving you an Inftance of a Wall, that is to be twelve Feet high from the Surface, or level of the Foundation before-mentioned. Every Foot your Wall rifes muft batter two Inches, then your 12 Feet high muft batter 24 Inches, and to this add 18 Inches for the Thicknefs of your Parapet, which will make three Feet fix Inches, for the Bottom of the Wall that ftands on the Foundation, and allowing at leaft three Inches for the fet-off, your Foundation muft be three Feet nine Inches broad; obferving that the back of the Wall is to be carried up perpendicularly, and the Stones laid firm, and after a Workman-like Manner againft the Bank, for if you only build the out-fide fair, and fill the back and infide care-lefsly, or perhaps, with a Icanty Allowance of Mortar, that Wall could not ftand long, let the batter be what it would. In order to carry on this Wall properly, you are to make a Plumb-Rule fit for the Purpofe, with one fide of it Plumb? and the other Side( 54- ) Side to fit the battering Side; but if you are carrying on a new Quay Wall of any confiderable Length, you ought to work by a battering Frame, always obferving, that the top of your Frame (which we fuppole to be i S Inches broad) be exadtly level to the level of the Bank, otherwife, you will find you will be either too broad or too narrow when you come to the Surface of the Bank; and indeed, all thefe rules ought to be obferved in building a Wall againft any other Bank. For fuppofe you build a Plumb Wall againfl: any Bank, which I have generally feen pradtifed, the Rain or Wet is continually carrying down a Quantity of loofe Particles, which become a Wedge between the top of the Wall and the Bank ; and like taking a Sword in the feeble of the Point, the further it goes the more Power it will gain, and thereby increafe its own Purchafe, till it at Length totally demolifhes it. November i ft, We began to put up the Centres for the two foutherly Arches, and prepared to do the fame for the Centre Arch. January ioth, 1 755, The Haunches of the two northerly Arches being compleated, we made a fafe and commodious Foot-way to the Dike, which we railed in, and which proved of great Advantage both to the Public and our Work. March 5th, The fecond South Arch was finiflied, and we began to build the crofs Walls from the Crowns of the Arches, in order to make the Carriage Way. Nftril 1 ft, The middle Arch being almoft clofed, we employed Men and Carts to bring in Rubbifh to raife the Pavement about the North End of the Bridge. 3d, The Paviour began to Pave. 8th, The laft and Center Arch being clofed, I immediately boarded in a Carriage Way of 20 Feet broad, over the middle of the Bridge, in order that the impatient Public might have the benefit thereof as foon as poftible; and on the fame Day, having got one Side of it paved, I invited the Right Hon. the Lord Mayor, being Alderman Percival Hunt, and the two Sheriffs to be the firft three* as accordingly they were, that were drove over the Bridge. I / \( 55 ) i oth, The Bridge was left open for the ufe of the Public in general, which made two Years and eighty Days, finee the Day on Yhich they were deprived of the ufe of the old Bridge, which was January 19th, 1753. EXPLANATION of Plate XVIII. Scale 40 Feet to 1 Inch. Shews you the fecond principal Operation with the thorough Foundation, Piers and Part of the Abutment to the Northward, and the new Coffer-dam on the South, on which I need not enlarge any further. EXPLANATION of Plate XIX. Scale 16 Feet to 1 Inch Fig. 1. Exhibits the Plan of the northerly Pier of the Center* Arch, ftanding on the thorough Foundation,^ which is laid over with large Stones, Hough and Ham, and fome pitched upon their Ends, and all of them wrought clofe and carefully bedded in Mortar, and the whole covered with a plentiful Coat of dry Grout, and that covered with a thick Bed of (harp Gravel, to preferve the Mortar till it Cements; on the Extremities of which, you fee Part of the two Rows of dovetailed Piles which are drove down to the R6ck, and cut off at the Surface of the Foundation, which is four Feet and a half under the Low-water Mark, as mentioned before in the Explanations of Plates XIII and XIV. Fig. 2. Shews the Center Arch, and half of each of the next adjoining Arches, compleatly finilfied, wherein note, A. The Rock in that Part of the River. B. Part of the natural Bed of the River. C. Thorough Foundation quite a-crofs the River, built as above and before-mentioned. D. Five Rows of Oak Piles drove down to the Rock, with a Grating of Timber on them, and wrought into the Mafonry. E. The like Grating of Timber under the foutherly Pier. F. Low, and G. High-water Marks. Fig. 3. This Figure reprefents Part of the Superftrudture, which extends 31 Feet from out to out of the Plinth of the Balluftrade. The Foot-ways are 8 Feet each, and the Carriage-way 31 Feet. This,( 56 ) This, according to my original Plan, was to be paved with Fire-Aone, in 5 or 6 Inch Courfes, each Cou'rfe to be fcabbled or rough punched at about i Inch or i l Inch convex, fo that the Feet of the draught Horfes might take a firm hold of them; and thefe Courfes were to be from 18 Inches to about 2 Feet in Depth, and fet with good clofe Joints in fwimming Beds of good Mortar, and for this pnrpofe I took Care to leave a proper Depth on the crown of the Center Arch. And now I hope that what 1 have offered concerning this Bridge fully exprefles every Thing neceflary for you to know concerning it. Tho’ the intended Brevity of this Work obliges me to be as concife as poffible, yet I think, I ought to embrace this Opportunity to relate a particular Incident that lately happened at this Bridge; but I muft firft recommend it to you to recoiled the covering I had laid on this thorough Foundation between the Piers, as mentioned in the latter End of the explanatory Notes on Plate XV. This laft Winter has been very remarkable for exceeding high Land-floods in this River, but particularly one that came fuddenly down from the Mountains on the laft Day of January, i 775, with iuch Violence, that it broke the Moorings, and carried off eight . Gabbards from the Coal-quay; five of them were flopped for fome Days by EJfex-lridge, and three of them carried diredly down the River; one of thefe five lodged againft the Sterlings of the middle Piers, and the Flood continuing very violent ten fucceeding Days, it was quite impracticable to get her off. As my young Reader may, perhaps, not be acquainted with the natural Efledls of fuch an Obftrudlion, it is neceflary to obierve, that Shoals or Sharps in navigable Rivers, have frequently been deepened and carried oft'by lodging loaded Gabbards quite a-crols them, becaufe they flop the Current at the Surface, and prcfs powerfully on the Water at the Bottom,- which confequently en-creafe the Strength and Velocity thereof, and fo break up and carry off the Bed of the R iver in fuch Places. But 1 fholl give a recent and more familiar Inftance: About ten Years ago, a rapid Land-flood broke the Moorings of a Raft of Timber at the Barrack-flip, and carried it down to Elueeii s-bridge, where( 57 ) where it unluckily lodged quite a-crofs the middle Arch. The Piers of this Bridge were built on the Surface of the Bed of the River, as moft of the former Bridges were. This Raft of Timber obftru£ting the Current of the Surface, in like Manner increafed the Power of it at the bottom, and within the Space of a few Hours totally demolifhed the Bridge. But to proceed. During the ten Days that this Gabbard lodged againfl the Sterlings of the middle Piers, I felt not the leaft Perturbation, but on the contrary 1 found my Heart exult with inexpreffible Pieafure, being thoroughly convinced, that if all the Arches were flopped up in like Manner for many fucceffive Years, that they would have no more effe£t on that Foundation than if it had been a folid Rock: However, after the Flood had fallen, Curiofity induced me to examine-the Effe£ts of it, and I really was furprized to find, that even the firft Foot Stratum of the covering which we laid over the Foundation was not in the leaf!: Degree molefted. Indeed, the upper Parts of the covering were by that and former Floods moffly wafhed away, but not ftripped of it intirely in any Place, and even if it was all wafhed away, yet the Mortar on the Surface of it is by this Time fo effeftually cemented, that the Current palling over it could not make the Jeaft Impreflion on it; and the red Firr dovetailed Piles that cafe and inclofe it down to the Rock (being in Water) will moft alluredly laft firm and found for numerous Generations to come ; and in the Interval, the Mafonry will in reafon-able Time cement to fuch a Degree, as if the Mortar and Grout of the whole were a£tually petrified, and even fo, as to put it out of the Power of Time to deftroy it. For thefe Reafons I moft earneftly recommend it to you, to do all in your Power to make thorough Foundations in like Manner, quite a-crofs fuch Rivers as you may happen to be employed in, that you may enjoy the like tranquil State of Mind, during the remainder of your Life, which I experienced when I faw the Gabbard lie a-crofs that Arch. I SECT.C 58 ) SECT. I. Concerning other necejfary Matters relative to the building of Stone-Bridges. I HAVE now cheerfully communicated a fhort account of.our Proceedings at EJfex-Bridge, and mentioned every Thing I thought materially neceflary for the young Student in the Art of Bridge-building to know, of which, the principal is the Ufe and Condrudtion of Coffer-dams; and I am fure he may by this Time form a clear Notion of their Utility in Works of this Nature, nor can I conceive the lead Idea of any other Way to lay fuch fub-ftantial and thorough Foundations as may.be done by their Means. I muff indeed, confefs, that the building of the Bridge, was attended with a great deal of Labour Night and Day, for upwards of two Years and a half fucceffively, but that was chiefly owing to the Foulnefs and Loofenefs of the Ground, which would not have been the Cafe, had we been working on clean and frefh Maiden Ground, for on fuch, there would be but few Difficulties to encounter with; and therefore, to prevent your being difcouraged, I mud; remind you again, that Mr. Labely was quite midaken in his Calculation (mentioned in Page 31,) for notwithdanding the exceeding great Roughnefs of our Ground, the Rapidity of the River, and the very great Depth we. were obliged to fink, and that the whole Circuit of of our Dams was much larger than what he would want for one of his Piers, yet, after we had got our Dams daunched, there did not foak for rfiany Tides fucceffively, (exclufive of the fubterraneous Water, mentioned in the 7th Chapter) a fingle Hogdiead of Water into our Pit, notwithdanding its exceeding great Depth; but it is not my Intention to leffen the Reputation which that great Artid has judly edabliffied, although to prevent your being difcouraged from fuch undertakings by what he has advanced, and for your further Improvement, I believe, without running the hazard of Cenfure, I might venture to make fome further remarks upon( 59 ) upon it, but I fhall leave that to your own Sagacity, by your comparing what he has faid\ to what we actually performed. When you come to Work upon frefh Maiden Ground (as I mentioned above) you will find no fuch Difficulties, but will have fure ready Work, even at the Depth we went to at the North End, and probably on “fuch frefh Ground, you need not fink much deeper than about three, four or five Feet under the Bed of the River, unlefs you intend to lay a thorough Foundation; but if you do not, that will be fully fufficient, provided you drive down fuch Piles as 1 have recommended in Plate i 5-, Fig* 4, all round your Foundation, till they get into firm Ground. In fhallow, frefh Water Rivers, the Difficulties and Expences attending this Manner of working, are quite inconfiderable; but you muft always obferve, that let the Water be what Depth it will, you proportion the Strength of your Dams to the Depth that you are to fink from the Surface of the high Water. In fuch Rivers as are under fix Feet deep, you may make your Dams very flight, excepting in fuch Rivers as are fubjedt to fudden Mountain Floods: Recoiled! what L. B. Alberti has left us (fee Page 9) which are, I think, the fullefl: and cleared: Diredtions I have mfet with, and according to the fame Manner which he there directs, I advife you to make your Dams in fuch Rivers as are under this Depth; but in fuch Water as is only about a Yard deep, one row of Stakes may anfwer your purpofe, and in ffiallower Water, Sods may prove fufficient; but be well prepared and extremely expeditious, lefl a Land-flood, fliould come upon you, yet, even if it did, the Expence would be but inconfiderable. There have been feveral Methods pradtifed by illiterate Country Mafons, who have built good rough Stone Bridges over fuch dial-low Rivers as thefe, and fome of them in much deeper Water. I fhall mention a few of their Methods; fuch as, ifl, Kefh-work, that is, a kind of large Bafkets, made of the Bofghs and Branches of Trees, about the fize of four or five Feet Square; thefe* they fink in rows, by throwing Stones promifcuoufly into them till they ground, and then filling them up till the Water is about Knee-deep, whereon they lay Timber a-crofs, and fo begin to build their Piers, I % banking( 6o ) banking the Kifhes all round with other Stones and hard Stuff thrown in, in like Manner. 2d, Reeve-work, that is, making large VefTels of red Deal Boards, hooped both with Iron and ftrong Oak Hoops, which they fill and fink in like Manner, filling the Vacancies between the Circles, and banking them round with the like rude Stones, fefc. 3d, Chef-work, i. e. making large Chefts of 5 of 6 Feet Square of red Fir Plank, dovetailed and clafped with Iron at the Angles, and thefe they alfo fill and bank in like Manner, which is generally among fuch Workmen deemed a good Method, becaufe they lie fo very contiguous to one another, and are very durable. 4th, Cafe-work, which is of the fame Nature, only much larger and ftronger, fome of them being 12 or 15 Feet Square, and filled and banked after the fame Manner. The 5th, is generally made ufe of by eminent Workmen in much larger Works. They call it Cafe-work, the French Caisson. They are made of large Timber, proportionable to the intended Ufe, and in Bridge-building, will admit of the whole Pier being built within them. Their bottom is a Grating of ftrong Timber, and their Sides of fquare Scantling and thick Planks, which are to be difengaged from the bottom, when the Pier is built within them to above the low Water mark, and then they are to be made ufe of for the next Pier. They are made perfectly ftaunch, and a Pit is drudged in the Bed of the River, as deep as they think fufficient, wherein the Weight of the Work finks thefe Cafes. All which Methods and feveral others, I moft minutely confidered before I defigned FJJ'ex-h ridge, and found that none of them would anfwer my purpofe; but having carefully pre-ferved my Remarks, Plans and Sketches on thofe various Methods, and at innumerable Times fince digefted them moft accurately, and alfo improved the Obfervations I made on the Petrifactions before mentioned; I apprehended and endeavoured to contrive fome others, which I prefume among us, may be called new Methods, which probably may prove more effectual in moft Cafes than any of them, which I have defigned to anfwer either in frefti or fait Water of very confiderable Depths, and which I fhall referve for the Subject of the fecond Part of this little Work. I am( ) I am fully convinced, that the Society of Artifts that have been lately eftablifhed in Dublin, through the generous Afliftance of the Dublin Society, has already proved of infinite Service in this Kingdom; and that fuch a noble Eftablifhment cannot fail in Time, to produce very ingenious and ufeful Men among us, many having already began to fhine forth in different Branches of Science, and particularly in Architecture. This, I think, inconteftibly proves that the People of this Country, have as good natural Abilities as thofe of any other, and were they to meet with equal Encouragement, there can be no Doubt, but they would carry the Sciences and the Arts to as great a Perfection; Encouragement being the kindly Sunfhine, which expands the budding Flowers, and makes them produce much good Fruit. The Guild of Merchants, as an Encouragement to that Society, moft generoufly paid 50 /. for the beft, 30 /. for the fecond bed, and 20/. for the third beft Defign for the Royal Exchange : And the Corporation of this City followed their laudable Example, in procuring Defigns for the Blue-coat Ho/pital. And there is no Doubt but when Ormond-bridge has fallen down, but they will continue to exercife the fame moil ufeful Generofity, and perhaps, much enlarge thofe Sums, as the Nature of that extraordinary kind of Work, and the preferibing proper and effectual Methods for laying the Foundations in particular, require a great deal of Labour, and juftly merit a very liberal Compenfation. Jn Hopes that many young Students in Architecture, may not oftly become Candidates, but actually merit the higheft Prize, I intend freely and fully to furnifh them with proper InftruCtions for that purpofe, to the beft of my Knowledge, but chiefly with re-fpeCt to the Foundation, and the principal Lines fuitable to that Bridge; but in order to exercife their own Ingenuity, I fhall leave the Decorations to themfelves. I have fhewn what a lofs I was at, and what infinite Trouble I had to find out and procure effectual Methods to lay the Foundation of EJfex^bridge. I have given a fuccinCt Narrative of the whole of my Proceedings in that Work. I alfo fet forth the good Fortune I had in getting Colonel Belidor\ Method of making Coffer-( 6a ) Coffer-dams, in the very critical Time I wanted it, for I had every Thing elfe to invent, to contrive and to reduce into order. The whole of thefe feveral Particulars you have now before you, and on a thorough grounded Knowledge I affure you, that the various Cir-cumflances relative to the re-building of EJfex-bridge that is done, and Ormond-bridge that muff foon be done, are exa£lly fimilar to one another, excepting, indeed, that the latter will be much lefs in ffze, and not near fo troublefome nor expenfive as the former; but I am very certain, there is no other Method to accomplifh it than that by which I compleated the other. The whole of what relates to the firft, and all that is neceflary for the latter, you have alfo now before you ready at Hand, without giving you the leaft Trouble to contrive or invent any Thing. And I hope my young Countrymen will now exert themfelves, and ufe their utmoft Endeavours to make themfelves Mafters of the Art of Bridge-building, and not lay the Corporation of the City, or other Gentlemen under a Neceflity of procuring Artifts from other Countries, when they have, or may have as fit Perfons for their Purpofes at home. C H A P. XL Concerning Ormond-Bridge, with the Soundings and Borings adjacent, and Remarks on the Bed of the River. IN theY ear 168 2, Sir Humphrey Jervis built a Bridge of Timber in this Place, which flood but two Years, which was, probably, partly owing to the injudicious Conftrudtion of it, or more probably to the intolerable foftnefs of the Ground it was built upon; but be that as k may, in the Year 1684, the Corporation of the City began to build the prefent Bridge. See Plate XX. Scale 20 Feet, 1 Inch. In April 1 752, this Bridge was in the utmoft Danger of fharing the fame Fate that Ejfex-bridge had fo lately met with; on which my Brother John and I were ordered to go and examine it, which accordingly we. did, rnd we found that the South Pier at A, had greatly lailed : The Bed of the River on which it flood was waffled aw ay, ✓ r 4 \ \ f •» i. \ * 4 \ 4 t I \ I IOV 2-C 63 ) away, and the firfl Courfe of the Stone-work alfo, for about feven Feet under the Pier, and Part of the fecond Courfe, and that that Part of the Pier had no fupport, but the Strength of the Mortar and the bond of the Work. This Difcovery induced us to examine the true Caufe thereof, in order to determine on the Methods for repairing it, which we could not effectually do without boring the Bed of the River, to find out what fort of Ground it was built on; and having at that Time made fome correct Soundings and Borings, and otherwife very ftrictly examined it, and having now the ^Drafts,* Soundings and Borings thereof by me, I do apprehend, that within fome very fliort Time, it muff inevitably fall; and as I am now fo healthful as to be able to reconfider them, it may be of ufe to the Public in general, and to the Corporation of this Hon. City in particular, to form fuch a Defign for the rebuilding of the fame, as fhall appear the moft eligible. For this Purpofe I here give the Public the true Soundings and Borings, fo far as we at that Time took them; wherein note, That the Dots under the Numbers of the firft 12, and oppofite to the other 12 Borings, are the Spots into which we bored. Our high Water mark at EJJex-bridge (See Plate XIX. Fig. 2. G.) was transferred by the level of the Water to this Place, allowing the fame ten Feet from low to high Water, although, in Fa£t, it is not juft the fame, becaufe the Bed of the River rifes higher the further one go up it. BORING | Feet. 1 9 Inches. 8 From high Water mark to the Bed of the River, S. Side* 8 0 Coarfe, loofe Sand or Gravel. 8 3 Soft blue fandy Loam, *5 11 Rock. \ C2 6 To the Bed of the River. 3 0 Coarfe, loofe Gravel. 10 3 Of foft, fandy, blue Clay or Loam. *25 9 Rock. »( 64 ) N’J Feet. Inches. 3 9 11 To the Bed. 6 3 Harder and coarfer Sand. 7 5 Soft blue Clay or Loam. 23 7 Rock. 4 15 0 To the Bed. 6 5 Coarfe, gravelly Sand. .... 8 0 Soft blue Clay or Loam. 29 5 Rock. 5 10 3 To the Bed, (North Side) r 1 6 Soft blue, fandy Clay or Loam. 2 1 9 Rock. 6 9 11 To the Bed. 9 7 Exceeding foft, fandy Clay or Loam. 19 6 Rock. 7 10 2 To the Bed. 9 7 Exceeding foft, blue Clay, or rather Mud. ‘9 9 Rock. ' 8 t 1 4 To the Bed. i O 0 Very foft blue Clay, or rather Mud. 2 I 4 I Rock. 9 IO 1 To the Bed. 8 2 Exceeding foft blue Clay, or Mud. 18 3 Rock. IO 9 2 To the Bed. 8 2 Exceeding foft Loam, or Mud. 17 4 Rock. i i 10 8 0 7 To the Bed. Exceeding foft Mud. N. B. The Men found this fo foft, that they thruft down the Rods in a Minute without boring, and they believed they could do the fame with a ten Foot Rod, after they were through the upper Cruft of Sand and Rubbifh. I l8 7 Rock. NQ.ia N®. la( 6S ) Feet. Indies. I 2 11 6 IO 2 . 2,1 :8 ‘ To the Bed. ' More ftiff and, coar fer. Rock. The dotted Line which inclofes the South Pier,' is the outward bounds of the Coffer-dam, which we made to'keep off the Water, till we under-pinned that Weft End of it, where we found that there was nothing fupporting the upper'Work, but the Bond of the Stones^ and the Strength of the Moftaf asv before-mentioned, for that Pier had not a Frame of Wood planked’ in the bottom, under nor round it, as the Piers of Ejjex-lridge had, but the bottom Courfe of it was laid on the naked Bed, of the River, as I believe all the reft of the; Piers are. Some of them have funk to the Eaftward, and fonie oft them, but. particularly .the North Pier, to the Weft ward, one. Foot nine. Inches; at B. nidre than at C.; and greatly diftocated that Arch, which I believe, has been rebuilt, for by the Courfes of the Stones in the Piers, it is evident that no Arch could poftibly ftand, 'when, one Erid of the Pier haft fettled fo much' more than the other,'arid co'nftdering all' thefe Bbfings together, it is foriiewhat’fiirpfizihg it'lias’ftood fo long.,. • ' g" The large Dotts''in the' dotted Like, were taken5 ill order to know the'different' Depths'"of the Water, TTehce toTklriulate the- Length 'of thcPiles for the Dam; but they alfo are.offome ufe’ now,’in giving us the’Depths of the Water from high Writermarkj' in thofe feveralTlacesf •' •’ •• f : N°| De pth. I Indies. HI 1 H BM'-r •::9;| 15 ■ ;5 ' | 16 | n 11 9 \ 17:112 9 1 18 ,12 3 \ N°.Jj: Depth. Feet. Indies. 19 1 1 1 3 20 : I2> 1 21 20 0 2 2 20 0 23i H 3 24! 1 9 3 ■ Remarks( 66 ) Remarks on the Bed of the River, See, Although we only pierced the Bed of the River in 24 Places, yet that was fully fufficient for our Purpofe, and indeed, I think, they are alfo pretty fufficient for my prefent Gonfideratioo, upon which I can fafely conclude, that the Ground oppofite Charles~ freet, (where the Bridge muft be built) is not able to fupport the Weight of a Bridge; and if you turn back and rs-'esamine the Borings of N°. 5, 6, 7, 8, 9, 10 and 1 r, you will coincide in Opinion with me; but I do not by any Means advife you to depend entirely on thefe Borings, but take a Carpenter with you at low Water, and let him bring a Hand-ipike pointed at one End with him, and a niae Foot Pantile-lath or a Quarter-four, and let him break through the Cruft of the Ground, by firft driving or working down the Hand-fpike 2 or 3 Feet, and I will venture to engage, that he can thruft down the Pantile-lath to the Rock, ,in any Place you pleafe to fix on thereabouts, efpecially at 9, 1 o and 11; nor need you have any other Implements to prove the moft Part of our Borings; and thefe Experiments will be of Ufc, and give you a true Idea of the Nature of the Ground you are going to build upon; and that will alfo partly difeover the Reafon that the Wooden-bridge before-mentioned, lafted but two Years, and excite your Admiration, that the pxefeut Bridge has flood fo long, without fuffering the fame Fate. I fhall now lay before you the principal Lines of my Defign of a Bridge fuitable to that Place, and effedual Methods for the Accomplifhment of it. C LI A P. XII. The principal Lines of a Defgn for Ormond-Bridge, with proper InjlrnBions for the Execution thereof EXPLANATION / Plate XXI. Scale 20 Feet 1 Inch. Fig. x. TOTE, A. The Rock, (fuppofed upon an Average to be ^ about 12 Feet under low Water mark). B. Part of the natural✓ % 1“ \ M • ✓ r / I V * % % > i( 6; ) natural Bed of the River. C. Thorough Foundation of Mafonry, (three Feet high). D. Low-water mark (three Feet above ditto. Foundation). E. High-water mark, (taken at 10 Feet on an Average). F. Pavement, (five Feet from the Soffeto of the Center Arch). From low Water mark to the fpring of the Arch is 6 Feet. Thence to the Soffeto of the Arch io Feet 4 Inches, and F. 5 Feet; In all 21 Feet 4 Inches. G. G. Pavement 19 Feet. Declivity 2 Feet 4 Inches in the Pavement from F to G. It may not be amifs here to obferve, that a great deal depends on a judicious ere&ing of the Sounding-boards. Try the Depth at feveral Ebbs, obferving that it is much more advifable to calcu~ late from the lowed Ebb, for fear of raifing the Summit of the Pavement too high, and be fure that all thefe Dimenfions agree together from your low Water mark. The next material Thing is to confider the Water-ways. The Voids and Solids, or the Piers and Arches of the prefent Bridge, and of this Defign compared. Prefent Bridge. This Defign. Plate XX. Ft. Inch. Ft. Inch, Plate XXI. Ft Inch. Ft. Inch. South Arch 20 0 0 0 South Arch 25 6 O 0 South Pier 0 0 11 3 South Pier - . - * c 0 5 6 2d Southerly Arch - 24 3 0 0 2d Southerly Arch - 2b 6 0 0 Ditto. Pier 0 0 11 10 Ditto. Pier - - • 0 0 6 0 Center Arch - - 27 8 0 0 Center Arch 31 0 0 0 3d Pier - - - 0 0 11 0 3d Pier 0 0 6 0 4th Arch - 2$ 2 0 0 4th Arch - 28 6 0 0 4th Pier - - - oj 0 i ro 1 r 4th Pier - 0 0 5 6 5 th or North Arch 20 0 ! 0 0 5 th or North Arch 6 0 0 Total “7. 1 , 45 0 Total *39 o 23 0 iV. B. Abutments 1 o Feet each. In fixing upon the Scite of this Defign, obferve that the middle of the Bridge mud be oppofite to the middle of Ckarles-jlreet, but not in dire£t Line with it, becaufe the River and the Street form an acute Angle, and the Bridge mud be on right Angles with the Current, other wife the Piers will incline athwart the Stream, which K 2 alwaysC 68 ) always ought to be avoided, ;as fair as other Circumfiances may rea-ionably admit of it'. Fig. 2. Shews the Plans .of the ' two foutherly Piers, and the Inclofure of the thorough Foundation, which mu ft at the leafl be ,50 Peet broad in the clear * of the Piles that inclofe it. Fig, 3. Shews vvhat the Stiperitrudlure will be when finifhed. EXPLANATION df?L AT e XXII. Scale 30 Feet 1 Inch. This Plate reprefsnts’-the* firft general Plan of Operation in laying the foutherly Foundations; .wherein note. A. Pool, for Pump Engine. B. B. Water Trunks. C. The Pit for building the South Abutment and Pier. D. Pit for building the 2d South Pier, : EXPLANATION of Plate XXIII. Scale 5 Feet 1 Inch. Fig. 1. Plan of the middle Dike of the Coffer-dam, through the Center Arch. Fig. 2.. Conftrudlion.of the Coffer-dam, wherein note. A. Low-water. ' B. Pligh-water. After the Frames are drove down as deep as you can drive them, they are to be drained together, fo as to give them a fix Inch batter in the middle row, and the outward Rows in the fame proportion as formerly directed. Confidering the exceeding Toft Ground on which this Dam is to be eredled, it is very probable, that after the Clay is put in them, they will be liable to incline either to one Side or the other, and whenever you can perceive that, or you obferve that the Clay Ipreads out the middle Frame, in either of thefe Cafes, and either within or without the Dam, you are to proceed after the fame Method already fully laid down in Plate VIII. C. e, f, g and h, explained in Page 32. EXPLANATION of Plate XXIV. Scale 5 Feet to 1 Inch. Fig. 1. I apprehend, that I have been fo explicit on Plate XIII. Fig. i. that I need not repeat here, as this Draught and Scale may fully£/ f •I / 1“ p r 0 V f \ * 1 n \ / t ✓ ✓ • fr * V A.  6> ‘ * \ ( 69 ) fully anfwer your Purpofes; only obferve, that G. Is the Superficies of the prefent Pavement, which is 25 Feet from the level of the bottom of the Pit; and if you find it necefiary, you may go another Foot deeper. H. Is the End of the Land-tye. Fig. 2. Section of the Land Abutment and -half of the South Arch, wherein note. A. The Rock. B. The bottom of the Pit, (unlefs you go another Foot deeper, as above-mentioned). C. The Surface of the thorough Foundation, which is here fuppofed to be three Feet high; but if you add the other Foot in Depth to it, do not forget that Foot afterwards in all your other IJimenfions. D. Low-water mark 3 Feet. d. Center from which the Arch was defcribed. E. Springing of the Arch. F. High-water mark, f. Soffst of the Arch which is 8 Feet 6 Inches, that is * of the fpan from E. to f. G. Surface of the Pavement. EXPLANATION of Plate XXV. Scale 5 Feet to 1 Inch Weft End of South Pier. Fig. 1. Is the Plan of the Coffer (or Inclofure of the inner Pit) for laying the Foundations. Fig. 2. Is the Sedlion of the fame. Fig. 3. Is the Foundation of the Weft End of the South Pier; wherein obferve, that there are five Piles in each row, at about 14-Inches afunder, and about three Feet diftance in the rows. In the North Piers of EJfex-lridge you may obferve they were four Feet afunder each Way, becaufe the Ground was there tolerably ftrong, but here it is intolerably foft, and therefore, it is requifite they lliould be drove clofer; yet we mu ft not depend too much upon the Piles, but endeavour to make the Mafon-work as fubftantial as poffible, in order to which, let me recommend the procuring good flout rough Flags fcabbeled to three Feet long (the Diftance of the rows the long Way) and after laying at the leaf!, half a Foot thick of fharp Gravel, covered with two or three Inches thick of Roach-lime over your Ground, bed thofe coarfe ftrong Flags upon it, which will fill the three Feet rows from Pile to Pile; then throw in Pieces of Flags, that will fill between the Piles the other Way, and from( 7° ) from thenceforward, let each Stone fwim in good ftrong Mortar, clofely and carefully wrought. Another Method may be this: Sink the . bottom of your Pit feven Feet under low Water mark, and allow the Foot before-mentioned to be filled with that Bed of ftiarp Gravel covered with Roach-lime, and then your Maionry will be three Feet as above. The Reafons for this will be hereafter mentioned. Fig. 4. Is the SeClion of the Weft End of the South Pier, and the Foundation on which it is to ftand: Obferve, to be fure of your Diftance from the Rock, before you cut your Piles to their Length, and let them be rather too long than too fliort, and in driving them (which will be eafily done) that every one of them goes down to the Rock: Cut them exaCtly fquare and level, fo that your Caps may lie firm upon them, and be careful, that your ftretching Beams lie firm and folid upon all your Caps. Thele ftretching Beams ought to be 50 Feet long at the leaft (as before-mentioned) if you can conveniently get fuch, that they may reach quite acrofs the Foundation: That is, the clear of the dovetail Piles that cafe and fecure it, efpecially the middle Beam, but the reft may be proportionably fhorter; and that the Mafonry be made level to the Heads of the Piles, take Care that the Caps may lie folid on them alfo: And the fame Care is to be taken when you are levelling to bed your ftretching Beams, and that the Mafons do moft punctually oblerve the Directions before given for them. The next Pier is to be done after the fame Manner. EXPLANATION of Plate XXVI. Scale 5 Feet 1 Inch, The Plan and SeElion of the North Pier fplringing high. The Bed of the River at this End of the Bridge, being much fofter than at the other End, you ought to endeavour to make them both alike ftrong: In order to which, I propofe that this Pier fhould ftand upon Piles, For if you recolleCt ‘ the eleventh boring, I believe you will conclude with me, that notwithftanding all the Care and Captions given tp the rough Mafons, their Work between the rowsPL Ground, put another entirely in Water, and keep a third in lome dry Place: Now I am confident, that each of thefe Blocks will in a reafonable Time actually petrify into Stone, and become as much i'o as if they had been cut or wrought out of a Rock, and that they will endure Calcination, and become good Lime afterwards, but not fo rich as that was from whence they derived: And with refpedt to Timer that which is depofited in the Bowels of its own natural Mother, will grow the fir ft into Stone; that laid in the Water, will be the fecond, and that which is. kept.in the dry Place, will be the laB and of a fhort brittle Nature: But. the flrB, if in a large Block, will not only become hard, but Bout and Bubborn, and would Band and give great Refi.Bance to a Hammer or Punch: The fecond, would be more free: And the third, fly off fhort. I apprehend that this little Experiment is worthy of Attention, be-caufe, by :afc'ertaining the Time of thefe DepofitSyland trying the Blocks from Time to Time afterward with a Tool or the Point of a Penknife, fome ufeful Knowledge might be obtained; but be that as it may, thefe are fome of my Reafons for recommending Lime-Bone. However, where that cannot be conveniently got, you muB make ule of fuch hard Stones as you can get, but be lure you have them broke to the Sizes above-mentioned, for fuch will moB afliiredly cement and unite together with the Lime and Gravel, and each of the Stones will contribute to fuflaim the Confidence repofed in them;; whereas, if one large Stone was put in among them, it Would not unite but Band up Bift, and thereby be a great Means of fhifting the Weight from itfelf, and throwing it on the finall Stones that lurround it, and.confequently would o^ifturn in-Bead of fupporting the Weight which it was deBined to bear. For thele, therefore, and many other RealonS, I moB earneflly recommend it to your Pra&ice, to ufe no other but final 1 Stones in youf Buffing. You are alfo to take particular Care, that your fandy Gravel is Biarp and clean, and of that Degree of Finenels as may contribute proportionably to the Solidity of the whole,, and not to throw ypuir Stones in one Place, and your Lime and Sand in another, but let them be all equally mixed throughout the Work, and all this nan N 2 be^( 92 ) be eafily done; for let the Water be of what Depth it will, or your hurry ever fo great, this you may do, and you are not to negleCt it. And obferve alio, that this fort of Work can be much more effectually done in Water, than upon dry Land, even admitting that it was to be done with wet Grout, becaufe thefe three Materials being thrown in proportionably together, each Stone and every Particle of the Gravel and Sand, will take Poflefiion of a Place fuitable to it; but the Sand in particular,, will continue in quick Motion till it finds out a place of reft proportionable to its Size* and inftantly fill up the moft minute Vacancy, (provided that you obferve thefe Directions properly) and., immediately become as compaCt and as folid as a Bank of a Gravel-pit that has been formed by Nature. But after all I have faid, you may, perhaps, imagine that this fluffing, even fo managed, will not be fufficient for our prefent Purpofe, without giving it a long Time to fettle and cement; and I grant it would not be amifs to allow it fome fhort Time, to give the finer Parts of the fluffing Time to fubfide, fupplying it with thefe finer Parts, till it will receive no more; and if thefe hard and fubftantial Materials are made folid and compaCl, and clofely confined together, how can they fettle or prove infufficient even before they are cemented? Now I afk you, do you believe, or did you ever hear any experienced Man fay, that clofe gravelly Ground was not a fubftantial Foundation ? And is not this in all Refpe&s, at leaft equal to it? Becaufe, it is actually Stone refting upon Stonew of different Sizes down to the minuteft Particle of Sand all compacted together into one folid Mafs. Palladio has furnifhed you with his Opinion in the tenth Page, and fays, u You fhould choofe u a Place where the Bed or Bottom is even and uniform, and is iC either of Stone or of Gravel, becaufe Stone or Gravel are excel-u lent Foundations in Water.” And herein lies the grand Advantage that will attend all thefe ProjeCts, /. e. they are to be executed in Water, and if we fupply the Water with due Proportions of this fluffing judicioufly, it will take great Part of the trouble from us, and will, as it were, difpofe of every Particle of the fineft Sand, and with incredible Expedition convey it into fuch Interftices and fmall( 93 ) fmall Pores, as it will find fit to receive it, and if it does not fit or get room in one Place, it will inflantly conduct it downwards by its own Gravity, till it gets it properly fettled, which I prefume, no human Art could fo effectually accomplifh; and I think it alfo ad-vifable to propofe the following Experiment. When this little flight Coffer is made and fluffed with wet Grout, to within five or fix Inches of the Top, level it fo that every Stone on the Surface, may come to a proper and equal bearing, and cover it all over with a Coat of Grout; expofe it then to the View of judicious Perfons, and get their Opinion of it, and then Floor it all over with cut Stone, after a Workman-like Manner: It will then effectually fuftain the Weight of the Statue,, which in this Cafe is the Thing required; but in order to fum up and finally determine the Utility of thefe Speculations,, which are in a large Degree the Bafe and Foundations of the following Pro-pofitions; let us particularly recollect, examine and confider wellr what Alberti has tranfmitted down to us; that is, w Upon pulling u down a very high and firong Tower at Bologna, they difcovered w that the Foundations were filled with nothing but round Stones-w and Chalk to the Height of nine Feet.” Let me, therefore, recommend it to you, to get a fquare Pit dug,, fuppofe of 9 Feet deep and as many broad, the Length at Difcre-tion, and let that be done near a Pump, or convenient to fome Water, and when it is filling with thefe Stones and fandy Gravel, fupply it moll plentifully with Water, to convey the Sand into all the Vacancies, but put neither Lime nor Lime-water in it, and when it is filled level to the Surface, throw more Sand and plenty of Water over it, and let the Men (with the back of their Shovel) beat down all irregular Stones, and make an even Surface as before mentioned, but do not then Floor it with cut Stone, but get fome Gentlemen or other fkilful Perfons to view, to prove and examine whether or no that is a fubffantial Foundation, whereon to ereCt the moft weighty Building immediately. And if it be given in the Affirmative, as moll certainly it will, then confider alfo, that if the Lime or Lime-water was properly compounded with thofe materials, then would the whole be endued with this great and remarkifele Advan-( 94 ) Advantage, viz. The longer it will ftand, the harder and more durable it will grow; and if the Pit was a Mile Cube and fluffed in like Manner, it would be all the fame in effedt. SEC T. IV. Concerning two other more weighty Purpofes to which thefe Methods may he applied in ft ill tVater. Prop. I LIT ET us fuppofe that a Gentleman has ' an elegant jf_j Vifto, terminated hy afpacious Canal, the Water in which is twelve Feet deep, and he requires a Foundation to he laid in it, whereon he intends to erect an Ohelijk of 36 Feet high. METHOD laid down in Plate XXIX. Scale 5 Feet 1 Inch. Wherein note, Fig. 1. Half of the Plan or Bottom of the Coffer, which is to be made of four or five Inch Plank. Fig. 2. Half of the Section. Fig. 3. Half of the outfide eredt, dovetailed and furrounded with 5 Belts, and Fig. 4. Half of the Platform which is floored with cut Stones of 4 by 2 Feet, and a Foot thick, a. The Rings for Hauling and fixing the Coffer, b. Brace Bars, Chains or Beams as mod convenient, c. Scite of the Obelifk. d. Plinth of the Pedeftal. e. Bank to confine the Lime-water. Let us alfo fuppofe, that a Nobleman hath a large Piece of Water adjoining his Pleafure-garden, from a particular Place in which, he and his Company have frequently been highly delighted with beholding feveral beautiful Profpedts, from his Pleafure-boat; and he has a very public Spirit, and is defirous to enlarge' the general Beauty of that highly improved Country, the better to enjoy the Benefit of the wholfome Air, lie is determined to have an elegant ©diagonal Pavilion or Pleafure-houfe, of 18 Feet Diamete;*, built in that particular Place; that the refpedtive Windows may, take in the Views of the natural Landfcapes;; And he alio apprehends, that when the Windows are fully illuminated, a Band of Martial I 9  * \ / ( 1F. 2 H H0 \cS^lSL VlI I mr.TramTiAiiiiiiili: PL i 30. \ \ : C TsT e G ;|= F 3 ¥ iitr\r.trTn: trtrtrwjrirsi \TXt±nx 4 ( 95 ) Martial Mule, &c.on rejoicing Nights, will contribute greatly toward the Amufement of the Nobility, - and the adjacent Neighbourhood. Therefore, Prop. III. You are required to build a Pavilion of cut Stone, in a Lake offrefa FPater eighteen Feet deep\ the Platform to be en^ clofed with a Parapet of the fame, extending 34 Feet fquare. METHOD laid down in Plate XXX. Scale 8 Feet 1 Inch. Fig. 1. Is the Plan or Bottom of one half of the Coffer. Fig. 2. Se&ion or infide of the fame as if it were floored with cut Stones. Fig. 3. Elevation thereof. F. Bottom of the Water. G. Surface of the fame. H. The Bank, and Fig. 4. The Platform floored with cut Stone of one Foot thick. Wherein note, a. Launching and hauling Rings, b. Reprefents the Situation of the Brace-bars, which in this Work ought to be much rather fmall Boom-chains, and Brace-beams alternately, c. Scite of half of the Pavilion, d. Walk, round the fame. e. Parapet-wall. » This Coffer is to be furrounded with a double Belt above, and three fingle Belts below them, as in the laft Proportion; and they are to be dovetailed and plaited with half flat Bar-iron. All thefe Belts are to be both bolted or fpiked to the Hull or upright Piles, and alfo pinned with Gak Trundle of about \ .Inch Diameter, which are to be driven in the outfide, and wedged within-hde. Both the upright Piles of the Hull, and all the Belts, you, may fee by the Scale, are to be fix Inches thick. The fluffing the fame as before directed, and to prevent Repetition, I ffiall omit feveral other Matters, which you ffiall be made fully acquainted with, through the Progrefs of the following explanatory Notes, which you are to apply according to your own Judgment. Let us now endeavour to point out another Method of working in Water, for inftance, in freffi Water Rivers. CHAP.( 96 ) G H A P. XV. Concerning another Method for laying of the Foundations for the Piers of Stone Bridges, in large and deep Rivers. ^TT^HERE have been various Methods pradlifed in laying the jL Foundations for the Piers of Bridges, in large and deep Rivers; but they have generally proved fo extravagantly tedious and expenfive, that the Public have been quite difheartened and deterred from even attempting fuch a Work, notwithftanding they labour under great Inconveniencies for want of them, efpecially in large Towns and Cities, and in all populous Countries, through which fuch large and deep Rivers run. Now I hope by this Time my Readers have been able to form fome kind of Idea, concerning what I mean by Coffers; and if fo, let us apply our utmofi: Endeavours to remedy the great Difadvan-tages which the Public are labouring under, by contriving fome other fure, quick and cheap Methods for that Purpofe; in order to which, I recommend it to you in the firft Place, to make yourfelf thoroughly acquainted with the Bed of the River on which you intend to work: Some, you muif be fenfible are hard, fome foft, iome partly confifling of both, fome are very fmooth and even, and others may have large Rocks or tumbling Stones, Me. You muft, therefore, make a firm Refolution, never to fit down to defign the Bridge, nor to confider the Conftrudtion of your Coffers, till you have moft carefully tried, and fearched diligently into the Bed of the River, which you may eafily do by the Methods formerly directed, let the Depth of the Water be what it will in Moderation : .And when you have collected and figured down your Soundings and Borings, you may proceed, and confider the grofs Dimenfions of the Bridge, and the Conilruclions of your Coffers. But I prelume, we may venture to eflablifh one general Rule, concerning Bridges in particular: i. e. To proportion the Bridge to the Depth of the Water; as for inftance, if the Water be three Fathom deep, your Coffer mufx be 19 Feet high, and at leaf: 1 8 FeetV I \ ) i l) j \ % ') H If 8 e h % ! i I H) Pt. SJ. 1 J( 97 ) Feet broad in the clear, and it will ftand as firm as a Cube. And you muft adhere clofely to Palladios Rule, which is, u that the u Foundation muft be as thick again, as the Wall intended to be u raifed upon it;” but you muft by no Means follow his next Direction, i. e. u to make the Foundation wider in foft loofe u Ground,” for that would make the Bridge quite preposterous; but you muft Strengthen the foft Ground with Piles to Such a Degree, as may bring it to an Equality with the reft of it, (as I did at the two northerly Piers of FJfex-bridge, fee Plate XIV.) I fay, if the Water is 18 Feet deep, your Coffer muft be at leaft i 8 Feet broad, and confequently the Pier 9 Feet thick; which (if executed as reprefented in Plate XV. Fig. 1, 2 and 3,) will admit of an Arch of 54 Feet Span; and it is my Opinion (with Sub-miffion to fome eminent Gentlemen) that the Breadth of a Bridge Should be determined by its Heighth alone, or that the whole Bridge taken together, muft bear fome Analogy to the Depth of the River; for the higher the Superftru£ture, the greater extent the Foundation requires; but as there are numerous Books extant on this Subject, you may confult them, and let us keep to our Text with refpefl to the Foundations of Piers, and on this Subjecft as before, we ftiall begin in Shallow Water. SECT. I. Prop. IV.IF P is required to build the Piers of a Stone Bridge, in jf a fr^fh JPater River of one Fathom deep\ the Bed of the River, Pam or Jharp and clean Jandy Gravel: Phe Proportions of the Bridge left to Difcretion. See another different METHOD laid down in Plate XXX f. Fig. 1. (laid down by a Scale of 5 Feet 1 Inch.) Reprefents the Section of the Coffer, and the Pier fpringing high, as if the Foundation had adtually been laid. Wherein note, A. Bed of the River. B Ordinary low Water in Summer. C. Conftrudtion of the Coffer, which is to hold the Stuffing, as for- O * merlyC 98 ) merly dire£led. D. One of the Brace Bars, which may be an Inch and a half fquare. E. Shews the Bond of the Cut-ftone-work of the Pier; and F. the banking. Fig. 2, 3 and 4, are laid down by a Scale of 1 Foot 1 Inch, and exhibits the Plans and different Views of the Piles, that are to com-pofe the Coffer, and after what Manner they are to be pointed, which may, perhaps, require to be burnt a little in the Fire; but in thefe Kinds of Beds they need not be fhod or pointed with Iron. This Coffer rifes one Foot above the low Water in Summer; but generally fpeaking, that Foot will be as if it was all under Water, according to our former Intentions. Now, the Coffer is eight Feet wide in the clear; becaufe, had it been made exactly cubical, the Pier would be but 3 Feet, which would be too diminutive; and for this and the like Reafons, you were not to be confined, as the Proportions of the Bridge were left to your own Difcretion. There are feveral Ways of making what they call dovetailed Piles, three of which I have given you in Plate XV. but I prefer N*\ 4. to any other fort that I have ever feen, becaufe it is fure, cheap and quick: the leaft gravelly Pebble will tear and fplit off the dovetails in N°. 5. and N°. 6. I ufed at EJJex-bridge\ but I found it to confume and waffe a vaft deal of Timber and Time, as I told you before. You fee in N°. 4. or in Fig. 2, 3 and 4, in the prefent Plate, the Tongue of one Pile falls into the Groove of-the other. The Piles I fuppofe to be 12 by 6 Inches, which is thicker than what is neceffary for this little Coffer; but if a flender Pile would meet with fliff Ground, it would not drive, and thefe will be pretty flout to bear a proportionable Force. The 6 Inches thick are divided into three Parts, two Quarters, that is Scantling of near two Inches fquare, forms the Groove, and another of the fame Size makes the Tongue, and are all put on with proportionable Spikes, Pins or Brads. Their Connexion will be more fully exhibited by the next Plate. — Plate XXXII. Fig. 1. Scale 5 Feet'to 1 Inch, Which is the Plan of that half of the Coffer that lies to the Stream, but the Stern of the Coffer may be about two Feet longer. The Linefe> ✓ 4 % ✓ f »C IOO ) drive at the leaft fix of thefe little fliort Piles in an Hour, and by having freffi Men to fucceed them every eight Hours in Summer Time, you may quickly difpatch the Coffer, provided, you have made proper Preparations for it as before directed, always obferving to lafh all the Piles you drive in the Day very tight, leaft an unexpected Rain ffiould come on, and for aught you know, bring down a Flood upon your Work; and in Cafe you have caufe to fufpeCt a Flood, brace your Cut-water Pile with temporary Braces, in the fame Manner of a. b and c. in Plate XXIII. and from thence difperfe the Braces to the right and two obtufe Angles of the item of the Coffer. SECT. H. Prop. V.ITT* is required to build the Piers for a Stone Bridge, in JL a fmooth frejh hVater River of fix teen Feet deep, the Bed of the River Loam; the Proportions of the Bridge left to Dif-cretion, as before. METHOD laid down in Plates XXXIII, and XXXIV. Scale 5 Feet i Inch. Plate XXXIII. Fig. i. Section of the Coffer. Wherein note, A. The Bed of the River. B. Ordinary low Water in Summer. C. SeCtion of the Coffer. D. SeCtion of the Pier fpringing high, ftanding on the Platform or Floor of cut Stone. E. The Bank to be ot the fame foTt of Materials of the Stuffing, Lime only excepted. Fig. 2. is laid down by a Scale of a Foot to an Inch. Wherein note, a. Is part of one of the Piles that compofe the Coffer, having the Groove ripped off the upper Part of it, to receive the Brace-bar. b. Part of one of the Belts that furround it. c. The Nut that fcrevvs it tight together, d. The Screw, e. The Brace-bar fallen down into its Place, and is to be keyed under the End of the Screw-bar, d. in which there is to be an oblong fquare Hole made to receive it. PlateV v 0 \ ■ A. m ev o( 101 ) Plate XXXIV. Scale 5 Feet 1 Inch. Is the Plan of the Coffer for one half of one of the Center Piers. Wherein note, A. Middle of the Bridge. B. Outfide of the Parapet, which from out to out is 47 Feet. The Center Arch is to be 48 Feet fpan. C. Firft Stone of the Cut-water in the firft projecting Courfe of the Pier. It may perhaps happen, that you may meet with fome Difficulty, by fixing your Chain-braces fo exactly, as to fall directly into the Joints appointed for them, and alfo, in fplicing the long Sides of the Belts, fo as they may not wreck in dropping them down; and if you apprehend that, then follow the Method laid down in Fig. 2. which fliews how the Belts are to lap and break Joints, by which you will remove all the Difficulties, and make the Coffer extremely fubftantial, by dropping down your Brace-bars in pairs, as you fee in this Figure drawn horizontally. But I muft give you a Caution, with regard to your fluffing this or the like Coffer. If you have a Bed of fliarp, clean fandy Gravel, your firft Stratum ought to be plenty of Roach-lime, in order to cement and petrify that Gravel, and then proceed with the reft as formerly directed; but in Cafe your Bed fhould happen to be fine, quick Sand, or foft fpungy Ground, notwithftanding youf piling the infid.e of your Coffer at 2, 3 or 4 Feet afunder, yet, in fome Cafes it may he very neceftary, before you put in your Chains, to make a Belt pretty large, and drive it down (as I told you Coopers wrought) to the Bottom of the Water, as f. in Plate XXXIII. and that will keep all tight together below, and the banking, E. is to extend from Pier to Pier, and ten Feet above, and fifteen Feet below the Point of the Starlings of the Coffers, which will there make a firm new Bed for the River. I recommend it to my young Reader, to bend his Attention tO' the Methods fully laid down in this and in the laft Propofitions,. and principally exhibited in Plate XXXI. as I am convinced, that it may prove very ufeful not only for building in Water, but alfo in quaking Bogs or Moraftes, that have fmooth penetrable Bottoms, but efpecially Loam or foft Clay. Remember then, when you are engaged in fuch Works, in a ftill or gentle running frefh Water, quaking Bog or Morafs of a moderate Depth, that you may make efte£lual( IO* ) effectual Coffer-dams, by driving down fuch Piles as thefe, anfwer-able to the Intention and Size of your Work; only obferving, that in forming the Angle, it will not be neceflary to make ufe of fucli grofs Scantling, as reprefented in Plate XXXII. Fig. 2. letter e. Becaufe Scantling of the fame Size of d. d. will anfwer efFedhially, by pinning and fpiking the Grooves on the corner Pile, and the Tongue on the next returning Pile, and all their Heads may rife two or three Feet above the Surface, and there they may be cut off level, and a Ribbon run a long the outfi.de of them, from whence you are to dovetail ftrait Beams or Braces of fmall Scantling to keep all tight together, whilfl you have Occafion for them; and when all that is done in a Workman-like Manner, then get the Water, Slough or Mud taken out, corking any Leakages that may happen to appear according as the Water finks; and when you have thus got the Coffer clear, {Lengthen the Bottom by driving down fquare Piles, or by laying a Grillage of Timber on it as before diredted, and thereon let the Mafons go on with their Work after the ufual Manner; and when they have brought up their Work to a proper Height, thefe Piles that compofed the Coffer are to be drawn out, and applied to another Pier or Part of the Work. Single Rows of fuch Piles, may alfo be extremely ufeful, in preventing or flopping fubterraneous Leakages or Ouzings under Coffer-dams, Dikes, Sluices, Flood-gates, Wires, Canals, Mill-races or the like; and likewife an excellent Method to preferve and to keep in the Ground that is under the Piers, either of a new or what remains under an old Bridge, provided they can be drove down, for thefe will take very little Room off the Water-way, and will be exceeding tight and clofe tongued and grooved into one another, which is much better than any Thing that can be done by fquare Piles. In fhort, I cannot exprefs the great Advantages which I apprehend, may accrue or be deduced from this Method. But in many Cafes it may be neceflary to drive two Rows of thefe Piles, leaving a convenient Space between them, which is to be filled up with good and well rammed Clay, and that will unite with the Bottom,, and make exceeding ftaunch Coffers, or would alfo,( l03 ) alfo, effedtually enable you to make ftaunch dry Docks, particularly where feveral of them are ranged contiguous to one another, either in Tide-rivers, or within an inclofed Harbour in the Sea. sect, m Concerning the building of Stone Piers, in a deep •''Tide-river, on a hard rough Bed, 1HAVE already obferved, and' every Body may know, that there is a vah; deal of Difference between the various Natures of the Beds of Rivers; and for that Reafon we muft invent fuch Methods, as are capable of being varied in fuch Manner, as may make them fuitable to our Purpofes; but as I aim at Concifenefs, I fhall neither perplex you with a Multiplicity of Proportions, nor deprive you of fufficient Room to exercife your own Ingenuity; and therefore, I fhall State my next Proportion, fo as to comprehend fome of the moll extraordinary and difficult Circumftances. Prop. VI. Let it be required to lay a Jure, quick and cheap Foundation for the Piers of a large Stone Bridge, in a fpecious Tide-river, greatly expofed to the Agitations of the main Ocean, the Bed of the River exceeding hard and rocky; in the Middle of which, there are fx Fathom deep of low fVater, whence the Bed rifes gradually on both Sides; the fpring Tides fome-times rife f our Fathom more\ the Size and Proportions of the Bridge, left to Difcretion, METHOD, fee Plates XXXV. XXXVI. XXXVII. XXXVIII. In which 1 purfue the Methods pointed out by the frfl three Propoftions. Plate XXXV. Scale 3o Feet to 1 Inch, Wherein note, Fig. 1. Reprefents the Platform of the Coffers, for one of the Middle Piers in two leparate Parts, with the Plan of the Pier upon them. Fig. 2.( 104 ) Fig. 2. Exhibits the Elevation of the Coffers, with the Pier fpringing high. Wherein note, a. the natural Bed of the River, fuppofe then, at the Dittances of b. b. you are to drop down Stones (none of them need be above a hundred Weight) in two direct Lines acrofs the River, by which you are to make two Stone Dikes or Banks, of 12 Feet high or more, thefe Stones are to be of all leffer Sizes down to fandy Gravel; and then you are to proceed and fill-up the Pit, that thefe two Dikes or Banks will form to the level Line, c. c. with very fmall Stones, Gravel and Sand, and as much Roach-lime as you can conveniently fpare for it, always obferving to throw the largeft Part of it next the Stream of Ebb or Flood, and at other Times you may convey it by large wooden Troughs fattened to the Sides of the Gabbards. This Line, c. c. is the Bed or Scite of the Coffers, and may be made higher or lower as other Circumftances may require. And according as the Coffers are fettled in their refpedtive Places, or at any ether Time when you find it moft convenient, you may go on with banking or filling up the Pit after the fame Manner, till you level it to the Lines, d. d. The low Water mark is e. And f. reprelents the Breadth of the Bridge from out to out of the Parapets, 54 Feet. And the Center Arch is to be 84 Feet fpan, as you will fee more particularly deliniated in the next Plate. Plate XXXVI. by the fame Scale^ gives you the principal Lines of the three Middle Arches. Wherein note, that a. is the natural Bed of the River, b. The Bed on which the Coffers are to ftand. c. The Bank or artificial Bed of the River, as before mentioned. d. Low-water, and e. High-water marks, f. The Pavement. I do not doubt but fome Readers may object, that thus railing the Bed of the River and thefe large Coffers, will dam and obftrudt the Current In anfwer to this, you may be very well affured, that in all deep Rivers, the Current runs principally, and with the greateft Velocity toward the Surface of the Water, ai d confe-quently, thofe can only increafe the Celerity, but cannot obftru£t the Current; and in fome Degree, this is alfo the Cafe in all Stone Bridges, and therefore, that Objection can have no Weight, be-caufe, it is evident, that no difadvantageous Conclufions can be drawn\»II \( r03 ) drawn from it, even were the Bed raifed to four Times that Height. But from thefe Obfervations you may alfo colledt other material Remarks, that perhaps, may prove indrudlive and ufeful to you in feveral Refpedts, concerning the Motions and Velocity of Rivers. As for inftance, Suppofe that for fome particular Purpofe, you are required to calculate and to make a juft return of the daily Quantity of Water any fmall River may produce during the Summer Seafon. Obferve then, that previous to that Calculation, you are to make dridt Enquiry, and to make yourfelf thoroughly acquainted with feveral Parts and Places in that River, and in all thofe Parts and Places to take correct Sedlions and Plans thereof, on which you are to lay down your Depths or Soundings, Briefly obferving the Surface and Declination of the Bed, and the Declivity and Irregularity of the Banks; and note, that the Fridfion that arifes from thefe, greatly contribute to leflen the Celerity of the Water. The Thread, that is, the Middle of the Current of the River, runs the freed, and is the lead retarded by thofe Obdacles; and that Thread, efpecially during the Time of a Fredi or Land-dood, is always to be found nearly over the deeped Parts of the River, and thofe deeped Parts are very variable, and produced according as the Declivity and Circumdances relative to the Bed and Banks may diredl; and in dead or flow running Water, this Thread cannot be difcovered by the Eye; and therefore, for thefe Reafons, I fay, you are to make yourfelf thoroughly acquainted with all the Parts and Places, where you intend to take the Velocity or Celerity of that Water; that is, how far it runs in fome certain dated Time, which is to be done by draining two parallel Ropes or Lines, acrofs the River at certain Didances from each other, flridfly obferving, how many Minutes, or Seconds a Bit of Cork or fome other fuch light Matter will take to run a certain Space, which you ought to try near each Bank; and alfo, in the Middle of each of thofe Parts or Places of the River, alfo Briefly obferving, whether or no, they are hadened or retarded by the Wind; and fo, after dimming up all together, you may be enabled to calculate the true Velocity on an Average, and thereby compute and meafure P the( ) the cubical Feet of Water, that you may reafonably conclude to pafs through and may be produced by it in the Time required, making father large Allowance for wafte, &c. There have been numerous Perfons involved in very ferious and difagreeable Circumftances, both of private and public Natures, on the Credit of fuch Calculations as thefe; efpecially, where they have much exceeded the Truth, and thereby deftroyed and rendered hopeful Schemes abortive, that might perhaps, otherwile have been attended with private and public Utility. Hence alfo, you may conceive fome ufeful Ideas, concerning the Motions and Velocity of Rivers in general, but diftinguifh and remember, that rapid Land-floods roll down and principally a£ts from the Surface to the Bottom in all deep Rivers, as I hinted above, and that when a Flood Tide flows into the Mouth of a River over a Ihallow Bar, it operates from the Bottom to the Surface, by damming up, and totally overpowering all the frefli Water that comes within its Influence. But to return. Now, I hope, I have furniflied you with general Ideas of the Nature of the Works, which you are going about; let us in the next Place, conflder the Conftrudtion of thefe Coffers. See Plate XXXVII. Scale 5 Feet to 1 Inch. Fig. t. Reprefents the Section of the Coffer; but obferve as before mentioned, that this Coffer would be too large to be made in one, and therefore, I propofe, that it be made in two feparate Parts. Whereon note, that a. is the Bottom, b. b. The double Sills between each pair of them ; the upright Planks that compofe it are to be placed ere6l, and are to be the Tenons of the Hull, and then they are to be pinned and bolted together, c. is the Keel or Middle Sill, and as probably you cannot get Timber long enough for them, you muff jun a breaking cut through the longefl: you can get, fcarf them to fit your Length, and turn them End for End, and bolt them firmly together with Nuts and Screws; between thefe, you are to grate the Bottom with two Courfes of fix Inch Plank, crofling one another. Both the upright and horizontal Piles of the Hull are to be tongued and grooved as in Plate XXXI. Fig. % and 3, and all of them to be pinned together at their Interfe&ions, and all the outward/ \ «( io7 ) ward or horizontal Piles are to be dovetailed at the Angles, and there plated with whole flat Bar; and there are to be five launching and hauling Rings at the three right and two obtufe Angles of each Semi-coffer, (as formerly directed in Plate XXX. letter a.) e. is the banking or artificial Bed of the River, which you fee rifes 6 Feet high all round the Coffer, reprefented by c. in the laff Plate, f. Low-water mark. g. Temporary diagonal Braces, to prevent its warping in launching. You fee thefe Braces have a Bears Mouth upon the upper End of each, and are to be fitted and nailed to the Ribbon, h. and when the Coffer is fluffed about two or thr®e Feet high, they are all to be knocked off, as of no further ufe. Though I have drawn the four Tiers of Brace Bars to be made of fquare Iron, yet if it is as convenient to you, I would rather advife you to make ufe of fmall Boom-chains for that Purpofe; but ufe which you will, it may be advifable to ftrengthen them with the fix Inch Plank, to go quite through, and to be dovetailed at each End, through the Hull that is through the upright and horizontal Piles; and you may obferve in Plates XXXV. and XXXVI. that I have only belted the Hulls as before, but on fecond Thoughts, I think it the fureff Way to let them lie as clofe to one another as they can, and fo I have reprefented it in this 37th Plate, Fig. r. which makes the Hull 12 Inches thick throughout. Fig. 2. Reprefents the front of the Pier ftanding on the Platform, or Floor of Cut-ftones, which covers and inclofes the fluffing of the Coffer, which muff; be run Home to the Hull of the Coffer, when the Ribbon h. is taken away. You fee, for the Reafons before given, that I keep as near as the Bond of the Work will.admit, to have the Stones of the Scantling of 4 by 2, and a Foot thick; and if you carry up the front of the Octagon in Afhler, they will anfwer effectually, but if in Ruffic Work, each Courfe muft be about 2 \ Feet high, including the Champhers, and k. is the Height of the Arch Stones, the which if rufficated alfo, the Champher muff run through the whole Soffeto of the Arch; but all this is beyond our prefent Purpofe; let us therefore, return to the finifhing of the Coffer. See P 2 Plate( io8 ) Plate XXXVIII. Scale 5 Feet to 1 Inch. Fig. r. Reprefents the refpe£tive horizontal Situations of the Chains, and the reft of this Figure fhews you the Surface of the Cut-ftone Floor, that is to finiffi the Golfer within the Hull. Fig. 2. Shews you the Scite of the three projedting Courfes of the-Pier, and the third Courfe of the Body of the Pier, and the Bond of the Work in that Courfe. In thefe fix Courfes, that together carry you to the fpringing, there may be three of the Courfes chained with two Inch fquare Bar, funk quite down into their refpedtive Courfes, and run with melted Lead as ufual. I have already *advifed that all the Cut-ftone Floor, or Platform, is to be carefully and clofely fet in fwimming Beds of choice good Mortar, and all the Joints with Tarrafs Mortar, and if you do not think that fufficient to withftand the Effedts of the Water, you may at any Time afterwards fcrape the Joints clear for about two Inches deep, and either fill them with melted Lead, or rather cork them with the fhavirigs of Lead, but only for fo far, as exceeds that firft projecting Courfe. ; The feven ftrong Lines, d. reprefent the Cramps, that are to cramp the Hull and the cut Stone Floor together, which you will hereafter find more fully defcribed; only obferve, that they are to be lodged in the fecond Courfe of the Stone. And now I have furnifhed you with an Idea of my Intentions, pray point out any one individual particular in this Method, that is attended with the leaft Degree or appearance of Impoffibility, or even of any extraordinary Difficulty. Surely, you will not pretend to fay, there is any Difficulty in making the two Half-Coffers, which may be put together by a very few Journeymen Ship and Houfe Carpenters, and a few Black-fmiths, with the Affiftance of a few Sailors and Labourers, in a Fortnight’s Time; and if you are required to ufe any extraordinary Expedition, you may eafiiy have them launched and fluffed within another Fortnight, provided you take proper Care to have every Thing you will want timely and conveniently provided, and that you have proper Crafts to carry in your fluffing, which by the Affiftance and Direction of your ten-buoy Ropes belonging to your two Semi-coffers, the Men may t I i i » / « $ \ i i * v * • V •» t. I''( ro9 ) may work at low or high Water, either by Night or Day, according as you find necefl'ary; and if this Coffer can be Ruffed within a Fortnight, pray might not another fet of fuch Men do the like Work within the fame Fortnight? Let us now compare fmall Things to great ones. We are very well affured, that Apollodorus compleated 'Trojans Bridge within the Summer of the Year of our Lord 104, and that the ten outward Piers were built on artificial Foundations, made by wheeling in vaff Quantities of large and finall Stones, and other filling (perhaps like the Ruffing fo much ufed by the Antients) but by all my InduRry I could not find out, by what other Methods he made the Foundations in the Middle of the Riv'er. Now if I was to prefume to enter the LiR of ConjeCturers, along with Tome great Folks, I ffiould conclude, that the Methods he took to build the inner Piers were, to rife or bank up the Bed of the River (of which you ffiall hear further) and to fet fuch Coffers as thefe thereon,, and from thence proceed with the Stone-work as ufual; (and 1 have already told you where to find the true Methods which he muR actually have taken) and if the Foundation of one Pier can probably be carried up to low Water mark in a Fortnight, could not twenty fuch fets of Men, do twenty fuch Pieces of Work in the fame Time? And if fo, where is the Wonder that Trojans numerous Army compleated that Work within that Time? Nor need you be afraid to compleat fuch an one as we are now projecting, we will fuppofe of 19 Arches, even within the compafs of the fix Summer Months,, if there was a Neceffity for it, and Money fuffi-. cient to carry it on, provided you had fufficient Time, and you had previoufiy provided and prepared every Thing you wanted for the Purpole, before you launched your Coffers. SECT.( no ) SECT. IV. Concerning Bridges principally contrived for the TJfe of Londonderry, Waterford, and Wexford, and for fuch other large and deep Rivers. ' | THROUGH the Courfe of my Endeavours to contrive and |L find out effectual Methods for building Bridges and other Works in deep Waters, Londonderry, Waterford and Wexford\ (each of which I have viewed) have conftantly enjoyed a prime Place in my Mind; and being thoroughly acquainted with many intolerable Difadvantages, that not only the Inhabitants in, and the Proprietors of thofe and the adjacent Places, but the Public in general daily fuftain, through their want of Bridges; thefe Confider-ations alone, have excited my moft zealous Endeavours to find out proper Methods to redrefs thofe Grievances, and not in thofe Places only, but in many others in like Manner; and with that Intent, I here freely tranfmit and communicate to you my Sentiments and Ideas on this important SubjeCt. And I am fure that they are confidered, and well weighed to the utmoft extent of my Capacity, and that they are not only practicable, but by a prudent Application of what I am now laying before you, may be productive of immediate Utility, and anfwer according to the Appellation bellowed on them, of being fure, quick and cheap Methods, for thofe and the like falutary Purpofes. The Goncifenefs of this Work, and not being able to procure proper S'eCtions of thofe Rivers, prevented my laying them down particularly, nor have I formed any Defign exceeding fix Fathom low Water; but I hope they moft clearly point out, Methods for building in a much greater Depth. As for inftance, let us fuppofe a River of fifty Feet deep at dead low Water, and let us examine, after what Manner our general Rules muft conduCt you to draw Defigns for that Depth. The principal of which direCts, a that ^ the Coffers fliould at the leaft extend to a Cube of the Water w'they( I” ) * they fland in; and that the Size of the Bridge ought to bear u fome Proportion to the Depth of the Water in which it is to ® ftand.” Now if the Water be 50 Feet deep, the Coffer muft at lead: be 50 Feet broad, the naked Body of the Pier 25 Feet, and confequently the Arch muft Span 150 Feet. I grant that fuch a Span would not by any Means anfwer for our poor Country, becaufe the Expence would rife infinitely above any Thing that we could have the leaft Hopes of accompliftiing. Now to remedy this, the Method is obvious, turn back to Plate XXXVI. and obferve the Line b. which is the Scite of the Coffers and diftant from a. but fix Feet, wffiich is placed in the Middle of the River. Now, we muft fuppofe a. to be 20 Feet beneath b. and let a. be fuppofed to lie as far as you pleafe either to the right Hand or to the left, and let a. and b. be either more or lefs than 20 Feet; the Method is, to raife up and make an artificial Bed of the River, with fuch fmall Stones and Gravel as formerly directed, till you bring it to the Line* b. and to extend it in Breadth on the Bottom in Proportion to its Height; and then every Thing elfe will fall in, in due order. Hence it is evident, that let the Depth of the Water be what it \yill in Moderation, the Rules may help to conduct you in drawing Defigns for any other reafonable Depth. But perhaps, after all I have faid, you may obje£t, that this banking or artificial Foundation would not be fufRciently Strong for the Purpofe. You have been repeatedly informed, that in building Trajan's Bridge, Slpollodorus had u the ten outward Piers built on .an a artificial Foundation, by wheeling in vaft Quantities of large u and fmall Stones, and other filling, after the ufual Manner of u carrying a Mole into the Sea.”—Let us here obferve, that our Hiftorian fays, 1 after the ufual Manner of carrying a Mole into u the Sea.” And that notwithstanding thofe Rivers are greatly agitated at fome Times by the Sea, yet not liable to be quite fo much fo, as u a Mole projetfted into the Sea,” whofe Surface is expofed to the Waves of the Ocean. Therefore, it is evident, that if this Method was Sufficient for fuch an enormous Bridge, Surely' there cannot remain the leaft Obje&ion againft the Stability of ours. But( ) But pray give me leave to engage your Attention in a more particular Manner. It mu ft be admitted, that this Country cannot afford to carry on any expenfive or very fumptuous Work for want of Money; but if we have a Scarcity of Money among us, I am confident, that we have fuch very great plenty of fmall Stones and Gravel, that in every navigable River in this Kingdom, you may be abundantly fupplied with thefe common and in a Manner in-figniftcant materials, and together with the Labour of a few Gab-bard-men and Labourers, fuch an artificial Foundation may be accomplifhed at a very fmall Expence; and that either of thofe three Corporations, with the aid of fome of the principal Proprietors adjacent, even in Cafe they got no help from the Public, need not in the leaft be afraid of compleating fuch a Work. And as thefe common Materials can be fo eafily procured, it will confe-quently follow, and the leaft Degree of Prudence will diredt you to raife the Bed of the River as high as you think convenient with thefe cheap Materials, in order to fave Labour and other Materials that would prove infinitely more expenfive. And thus reducing the Depth of the low Water, perhaps to eight Feet, allowing four Feet of that for the Banking, and four for the Navigation; you are thereon to build the Bridge, according to the Plans and Methods hitherto and hereafter exhibited, or according to any other Proportions, that you may think moft agreeable to their refpedtive Situations, paying due regard to the Heights of the Banks, Quays, &*c. and particularly obferving, that the higher you raife the Bed, the lefs Money you will require to build the Bridge; but I fay you muft pay due regard to the Navigation of the River above the Bridge, for if you leave low Water deep enough for that Purpofe, you need not icruple in fome Rivers, to raife the Bed fo, as to reduce that Part of River to a perfedt Ford, -which all People fearch for that are concerned in the like Work, and which, yoii may make perfedlly fub-ftantial, if you adhere to our former Conclufions. Therefore, if Nature has not provided a Ford agreeable to your Purpofes, you may have it in your own Power to fupply that by Art, which you find you cannot enjoy by Nature. Hence you may alfo deduce an excellent Method of making or rendering a dangerous Ford, much more( ”3 ) more fafe for Travellers, even for Carriages of any kind, and the Expence will be but a Trifle to a County, where they might not be able to build a Bridge. Thefe brief Conflderations, I thought previoufly neceflary to prepare you to form a clear Conception of the particular Methods which I have contrived for, and I advife you to lay them before the Gentlemen of your Committee, but that fhall be the Buflnefs of the next Sedlion. S E C T. V. On an exceeding cheap, and mofl fubjlantial Method of building a Bridge, in .a very deep and fpacious River, which may be grafted on any of the fonner Methods. HAVING fully proved and demonftrated on the flx Propo-fitions, fo far as the Nature of my prefent Deflgn requires, that thefe are eligible Methods to build Stone-bridges in deep Rivers; it is incumbent on you to make yourfelf thoroughly acquainted with thefe Matters, and to apply your Attention and the utmoft extent of your own Genius, to confider and improve them according as you And it neceflary: And after all, you may probably find yourfelf far fhort of Arguments fufficient to fatisfy every Member of your Committee, which are generally compofed of Gentlemen of various Abilities; fome of whom, may perhaps, readily conceive and approve of what you offer, but others, may differ widely from them. Jn this Cafe, I advife you to enquire among your Acquaintances, and take Notice yourfelf, which of the Gentlemen feem to be beft acquainted with the furprifrng Performances of the Antients, in Works of this or the like Nature; for fome of thefe will be the mofl likely to fupport your Arguments, and this may incline the Majority in your favour. But fuppofe you fail herein, I have ftill a powerful Argument which cannot fail of meeting with the Attention of the Board, viz. that you fhould proceed with your Coffers, by either of the Methods Q* ’ pointed( ”4 ) pointed out in the laft Sedlion, which will bring your Foundation?, that is the Lip of the Hull, one Foot above the low Water mark, as reprefented by d. in Plate XXXVI. and thereon eredt Piers either of hewn or rough Stone, or both juft as they agree, which would fufffciently'anfwer your Purpofe, arid which you may begin upon the Platform, Plate XXXVIII. Fig. i. But it would do beft to begin them on the fpringing Courfe, reprefented in Fig. 2. and alfo in Plate XXXVII. Fig. 2. and thereby to make a fubftantial temporary Bridge with Timber, at fuch a trifling Expence as would not be worth Notice, in Comparifon to what it would coft, if done in any other Method that I have ever heard of. This Thought^when firft fuggefted, adluated by the Motives before mentioned, adlually carried me beyond the Limits of my former Intentions, which related to laying Foundations in Water only. However, I indulged it fo far, as to endeavour to furnifli you with a Defign of fuch a temporary Bridge, as may perhaps, fully anfwer the moft fanguine Expeditions of your Board and the Public; and which I fhall defcribe and demonftrate, on the follow-? ing Propofttion. P r op. VII. Jim are required to lay down fure, quicl and cheap Methods, for the building of a ?noft fubftantial temporary Bridge, with Stone Piers; the Arches (or the Spaces between the Piers) are to be made of Ti?nber\ the River at fome fpring 'Tides is ten Fathom deep, as was more fully dejcribed in the laft Propofttion. METHOD laid down in Plate XXXIX. Scale 12 Feet to 1 Inch. Let us here fuppofe, that the Coffers are fluffed and floored over with xut Stone, as reprefented in Plate XXXVUI. Fig. 1. on which you are to be determined, whether you are to go on with the cut Stone Work to the fpringing Courfe, as Fig. 2. and alfo Fig. 2. in Plate XXXVII. or whether you are to begin the temporary Pier on the Floor or Platform of cut Stone; but I fliould advife you to the former, becaufe it will be better, and there will be fo much done for the next Generation; but in either of thefe Cafes, obferve, that PlateI4 I( m> Plate X'XXIX. is defigned from the high Water mark of the lait Proportion, and extends to half of the two middle Piers. Wherein note, e. Is the high Water mark, which is the fame of e. in Plate XXXVI. and in both. f. Is the Surface of the Pavement, g. The lower, or principal Braces, which ought to be made of found hearty upright Oak, of 18 by 12 Inch Scantling. And the King-poft, h. may be the fame; but all the reft of hearty and found red Fir. i. The Collar-beam. k. Principal, 1. and m. The two main Braces, n. and o. The principal Beams, which you fee lie one upon the other (but it would be advifeable to lay Slips of found Oak Plank between them, upon a flant, to turn off the Rain Water, and particularly the out-fide ones, to keep them from rotting) Thefe four, gjfpS 1. m. n, and o. Are to have breaking Cuts run through them, and turned End for End, and then bolted together, provided that your Span is as great as this. The Prick-pofts p. and q. are defigned to fhorten the bearing, and unite their Strength. All thefe, that is, i, k, J, m, n, o, p, q, are to be about a Foot fquare; and each of the Frames are to be placed about four Feet diftant from .each other, the outward ones are ,to be tried up, The crown Beam r. is 18 by 12 Inches. The flooring Joifts which lie on the Beam, o, are to be nine Inch Scantling, and /paced at 18 Inches afunder. On thefe Joifts the flooring Planks are. to lie, which are to be fix Inches thick, this Floor may be fir ft covered with Pitch and Tar, and then with common Slates, and one or two Courfes of Bricks on them, laid in fwimming Beds of choice Mortar, clofely wrought and grouted. Thefe Slates are to preferve and prevent the Mortar from corroding the Planks, and over the Bricks lies the Pavement of the Carriage-way,, f. for which fee Plate XIX-Fig. 3. and the Foot-ways may be the .fame as. therein alfo delineated. Thefe Slates, Bricks, and Stones, if properly executed, will efle >C Ir9 ) METHOD laid down in Plate XL. Scale 8 Feet to i Inch. Fig. i. Reprefents the Sedtion of the Mole, wherein note, A. is the Surface of the Winter Water, which is 9 Feet deep to B. The bottom of the Water. C. C. Two Rows of fquare Piles, to be ffieeted on the infide with 1 \ Inch Plank, which mud be ledged together, and floated in on Edge between the Piles and temporary Poles, to keep the Sheeting upright in its Place till the Stuffing is put in, and then the Poles are to be taken away. D. The Chain that Braces both Sides together, which need not be very ftrong as thefe Piles are battered. E. The Road or Surface of the Mole, and F. The Bank of any common filling. Fig. 2. Is part of the Plan of the Mole with the Sheeting on the infide, and the double Ribbons on the outfide of the Piles (like Fig. 2. Plate XXXIV.) with the Chains that are to ftrain them in, and keep them to their batter, which may either be very flrong Plow Chains,- or Inch fquare Bar Iron, &c. You are to begin your Stuffing and Banking at the Shore, whence you are to be fupplied with it, and to carry them both on together, and your Carts and Cars having fufficient Room, they are all to come in on the right Hand, and return to the left, to keep them from interfering; and whilff this is doing, your Carpenter is going on with another range on each Hand before them. If this lies within View of the Gentleman’s Floufe, probably you will be required to enclofe it with Chinefe Rails; for which Pur-pofe, you are to prepare your Polls as diredted in Chap. XIV. Sedt. 1. and drive them down by the Sides of the Heads of the Piles; but if it lies remote, you may drive down flrong rough Stakes, and plat them with the Branches, for this is only a temporary Work, and there ought not to be much Money expended on it, becaufe, if it conquers, and effedtually keeps off the Water, the Gentleman, or the Public, or both, may be, perhaps, better accommodated with a fubftantial Road, or Imbankation. After you have fully confidered the next Propofition, or by the Directions formerly given for Quay Walky you may build a double Wall onon the reclaimed Side, at any convenient Diflance, and this will perhaps, effectually keep the Water off from you in the mean Time; but let us alfo fuppofe, and lay down Methods for making a fubftantial Turnpike Road, through a fhaking Bog, which may happen to intervene, and ereCt Forts or other weighty Building in the fame. S E C T. II. The Method of making a fubftantial "Turnpike Road, through a quaking Bog of 15 Feet deep, and to ereffi Forts or other weighty Stone Buildings in the fame. WE are informed that many fuch Roads have been made by the antient Romdns, fome to the extent of feveral Miles in Length; but in our poor Country, we have no right to pretend to copy after, them; but as Neceflity is the Mother of Invention, let us try if we can contrive to form a Method of accomplifhing a Work of this Nature, which is fo abfolutely neceffary, not only for the reclaiming fome of our Bogs, but alfo for the uniting the Neighbourhoods of two fertile Countries, that at prefent feem as remote from one another, as if they were in different Climates. As for Inftance: Between two very populous Countries, we will fuppofe, there lies a Valley of many Miles in Length, the greateft Part of which is liable to be covered with Water in the Winter; and even in the Summer, it is fuch a quaking Bog, as deters either Man or Beaft from venturing upon it: The Public have therefore, taken it in Hand and tefolved, Prop. IX. To make a fubftantial Turnpike Road, through a fhaking Bog of 1 5 Feet deep, to be inclofed with parapet TValls of rough Stone and Lime, of Jive Feet high on each Side, and 30 Feet broad in the clear. In Summer Time, this Bog is generally covered over with a Scraw, or Scurff of mojfy Grafs, under which the Sluich is 1 exceeding foft, that a Stone of one Pound JUSught will meet no Oppoftion, dill it finks to the Bottom, which is a ftiff fandy Marl./ / \ ( *21 ) Surely, you mull allow, that above all other Works, thole that are done by the -Public, ought to be performed after the mo ft fub-ftantial and durable Methods: Let us therefore, now coniider how this Work may be fo accomplifhed. See METHOD. Plate XLI. Scale 8 Feet to i Inch. Fig. i. Exhibits the Sedlion of the Road. Wherein note, A. Is the Surface of the Bog. B. The Bottom of it. C. The Dovetail Piles that form the Coffer. D. Temporary Piles or Planks that are to feparate the Stuffing. E. The Coffer for the Walls; and F. the Coffer for the Road. E. is to be fluffed with fmall Stones, Lime and fharp clean Gravel, as before diredled; but F. is to be fluffed or filled with the hardefl gravelly and ffony Stuff, you can conveniently get. Then the Planks D. are to be drawn up, as of no further ufe in that Place; becaufe the Stuff that is to make the Road, would not by any Means be fufficient for the Foundations of the Parapets. And you fee the fluffing E. is to be covered over with cut Stones of 4 by 2 Feet, and a Foot thick ; and hence you fee the Parapets are battered to 18 Inches thick. The fluffing of both E. and F. will fettle confiderably, but they will fettle perpendicularly, and drive and difperfe the Slutch of the Bog before them; and according as you find them fettle, you mufl ilill continue to fill them up from Time to Time, as Occafion may require, f The Chain that braces them all together. G. Parapet Wall. H. Surface of the Road, which you fee is here fuppofed to be but one Foot above the Surface of the Bog. I. Is the Banks which are to be raifed at Difcretion according as you go on, to help to Buttrefs and Brace in the Piles that form the Coffer. Fig. 2. Is Part of the PI ans of the Coffers, with the Situation of the Braces. In which obferve, that the Brakes are pM:ed together in Pairs, which may have about ten Piles between each Pair, as before directed in Plate XXXIV. Fife,; 2. I do not'pretend to fay, that this Method ft; entirely of my own Invention, but to my Succefs in confulting feveral undent Hiilories, wherein I found fufficient Matter, together w ith what R I have( 122 ) I have before mentioned, for my grounding this Contrivance, not only for the prefent, but alfo the following Propofition upon. And notwithstanding I take great Pains to be concife, yet, I fhall refer you to one particular Place, which you will find abridged in Chambers s Dictionary, under the Article of Road, which I before mentioned, and as that Book may not be in your Hands, I fhall here tranfcribe exactly what he fays. a Road, an open Way or Paflage, forming a commodious u Communication between one Place and another. 44 The Romans of all People took the mot Pains in their Roads. 44 The Labour and Expence they were at, to render them fpacious, u ftreight and Smooth, are incredible. — Ufually they Strengthened 44 the Ground by ramming it, laying it with Flints, Pebbles, or “ Sand; fometimes by a lining of Mafonry, Rubbifh, Bricks, 44 Potfherds, &c. bound together with Mortar. u F. Meneftrier obferves, that in fome Places in the Lyonnois, he 44 has found huge CluSters of Flints cemented with Lime, reach-44 ing ten or twelve Feet deep, and making a Mafs as hard and as 44 compact as Marble itfelf, and which, alter refilling the Injuries 44 of Time for 1600 Years, is Still fcarce penetrable by all the 44 Force of Hammers, Mattocks, &c, and yet the Flints it con-44 fiSts of, are not bigger than Eggs.”—Pleafe to obferve, that this coroborates with the former Accounts given of the petrifying Qualities of thefe Materials. I do.not fay that this Road of ours, will be as firm and as fub-flantial as thefe Roman Roads, becaufe we only purpofe to Stuff the Coffers on which the parapet Walls are to Stand, with thofe choice Materials; but I affirm, that if we were able to go to the Expence of fuch a Work, and this Bog was 20 or 30 Feet deep, it is practicable to make a Road through it as firm and as compact as theirs; f becaufe I am fure our Country abounds with as good Materials for that Purpofe, as perhaps, any other produces, except the principal Material, Money, to carry on fuch a Work. But notwithstanding our great Scarcity of this principal Material in all Works, yet Matters, perhaps, might be fo managed, as to carry on a ufeful Work of this fort at a very moderate Expence; and( I23 ) and here we have a fair Opportunity to introduce one of the Methods I pointed out, in the latter End of the fecond Section of the lad: Chapter, which I advife you to recall to your Mind, and I fhall now enlarge a little further upon it. If fuch a Road is to be made through fuch a fhaking Bog, you are to make fuch Coffers as is therein before directed, and exhibited in Plate XXXI. and throwing out the Slutch, Me. build a flender Pier in each of them of rough Stone, for about a couple of Feet above the Surface, and thereon to turn flight rough Stone, or hard Brick Arches, agreeable to the extent of your Defign; and as you go on, draw up the Piles and apply them to the next Piers in like Manner, as alio therein before mentioned; and to facilitate the Work, you may have feveral lets of fuch Piles. If Stones are fcarce and Timber plenty, you may make a fubftantial temporary Cauley over the Piers, but by all Means I would prefer the Arches. It is well confirmed that numerous fuch Caufeys, have been made through Morafles by the Antients, and that fome of them have extended to eight Miles in Length, and thirty Yards in Breadth. Numerous Forts and other fumptuous Edifices, have likewife been eredted by them in Morafles; but the Concifenefs of this Work, will not admit of my tranferibing Abftradfs from them. Let it therefore fufHce, that I here briefly point out one of the Methods which I firmly believe mud; have been the Method pradtifed by fome of them. And I alfo conclude may mod: readily be executed at a very moderate Expence by us alfo. As for indance: Let us fuppofe, that you are required to preferibe quick and cheap Methods for building a fubdantial Foundation for a Fort, or any other weighty Building of Stone and Lime of 200 Feet fquare, or any other large Extent, in a Morafs or quaking Bog ©f 15 Feet deep, on a penetrable Clay or loamy Bottom. Having thoroughly examined the intended Scite, and prepared Plans and Materials for the Purpofe, by this Method (fo fully explained above) you are to er-edl a competent Number of Pillars of ilrong rough Mafonry, fuppofe of eight or ten Feejilquari:, and perhaps eight, ten or fifteen Feet Didance from each other, and thereon turn fegment Vaults and Arches, wljch will give vou a R 2, Platform,( 124 ) Platform, whereon you are to- eredt the intended' Building,, always: paying due regard to the Pillars throughout the Superllrudture. This Method is fo eafily underftood, that I need neither form any Defigns, nor enlarge any further on it/ But I fhall give you another In fiance, in which this^ fort of Coffer Work may alfo in many Cafes be fuccefsfully applied, and have alfo been probably made ufe of by the Antients, in making inland Navigations through their Moraffes. SECT. III. Coffer IV:rk applied to the making of a navigable Canaf through a Jljakwg Bog 15 Feet deep. ^IT^HE Valley before-mentioned, extending on almofl a dead 1 level, for great Part of the Space between two navigable Rivers, with feveral opulent Market-towns adjacent; we will fup-pofe, that the Public have alfo taken in Hand, tQ turn the fame to a national Advantage, and refolved, Prop. 10. Fo ?nake a navigable Canal as a Communication between thofe Rivers, through the mofl convenient Parts of the Valley. You are, therefore, required to lay down fure, quick and cheap Methods to carry fuch a Canal through Part of a Jhaking Bog7 fifteen Feet deep, as before. See METHOD. Plate XLII. S’cale 12 Feet to 1 Inch. Fig. X* Reprefents a Sedtion of the Canal. Wherein note, A. Surface of the Bog. B. Bottom of the fame. C. Dovetailed Piles that form the Coffers, after the Manner of Figure 2, 3 and 4, in Flate XXXI. D. Brace-bars, Chains, or Scantling, and E. Bank, which is to be raifed at Difcretion. Fig. 2. Reprefents the Plan of the fame, fhewing the four Rows of Piles, Chains, Ribbons, Me, Thefe laft two Propofitions, if properly attended to, may alfo be produdtive of fure and effectual Methods of reclaiming extenfive Bogs,44 •V • » ftC 12 5 ) Bogs, and thefe Methods may be effectually applied to 20 or ?o Feet deep if neceffary, and are fo eafily underflood, that I need not enlarge upon them. But before Lconclude frefh Water-works,r I think- it advifeable to point out one' Advantage, that may accrue in the Way of Trade and Commerce, particularly to fucK Merchants as traffic in foreign, unimproved Countries; that is, to make either temporary or durable Quays, or to run out Tongues or double Quays, into fuch Rivers as belong to their Settlements, and that at a trifling Expence. For which Purpofe, obferve, that if the Bed of the River be hard or rough, you are to defign the Coffers purfuant to fuch Methods, as are deducible from Plates, XXVIII. XXIX. XXX. XXXV. XXXVI. XXXVII. but if foft and loamy, then you may purfue fuch Methods as may be colledted from Plates XXXI. XXXIII.-XL. or XLL and from the explanatory Notes thereunto refpedlively belonging, together with what you will hereafter find defcribed; always obferving, to proportion the Coffers to the requifite Depth of Water,' and in durable Work, on thefe Coffers you are to begin the Quay Walls as formerly directed; provided, Stone and Lime can be conveniently obtained; but if fuch cannot be procured and' that Timber abounds, you may make temporary Quays, of fuch Pleights as you think may anfwer your Purpofe: And obferve alfo, that by thefe Methods, you are to make Quays for launching your Coffers, &c. In Hill Lakes or fmooth running Water, you may eafily contrive by thefe Methods, to run out temporary Tongues or double Quays with Timber, to fuch Height and Lengths, as to afford likewife a Harbour for fmall Veilels; but by no Means attempt it in any Place that is liable to be greatly agitated, except you have cut Stone from near the Surface of low Water; but I need not enlarge on thefe Matters in this Place, as I intend in the following Sheets to treat largely on iqch Harbours, as will be abundantly fufficient to withfland the Violence of the moll turbulent agitated Sea. On which Subjedl, we (hall ffrll begin by laying down Methods to build a Beacon in fhallow Water. CHAP.( 126 ) CHAP. XVII. Coffer-work applied to Buildings, that may he thereby effectually executed in the Sea. I HAVE had, very little Acquaintance with Marine Affairs of any kind; and therefore, I prefume, I may hope to meet with fomewhat of Indulgence in my treating on Things of this Nature, and alfo for your own friendly Endeavours to aflift me, in hopes of bringing thefe important Matters to fome Maturity; as I have already infinuated, that thefe are but few Arts or Sciences, that have been brought to Perfection, by the utmoft Endeavours of the firft Contrivers of them. It is now upwards of 23 Years, fince I firft obferved the Petrifactions mentioned in Chap. VI. Sedt. 2. and from that Time to this, I have applied my feeble and utmoft Abilities, in endeavouring to turn and improve my Obfervations to the real Advantage of the Public in general; and I think, it would be inexcufable to {mother or conceal the Notions that occurred thereupon. But I entreat a patient Attention to what I am now about to mention, and I hope that my Plans and Defigns will not be condemned as impracticable, until the real Merit of them are thoroughly weighed and confidered; though 1 mull; confefs, that if ever you have feen the Sea in a violent Storm, as I have feveral Times obferved with a trembling Heart, I ought not to wonder at your entertaining fome Doubts of Succefs, but at the fame Time do not forget, that the Sea is not at all Times fo violently agitated; and therefore, let us endeavour to contrive fuch fure Methods as may reafonably promife Succefs, and be accomplifhed with great Expedition, at any Time when a favourable Opportunity offers; for it is not the Sea alone that you have to encounter with, but the moft aftonifh-ing and dreadful Effects of the Tides and Winds. As to the ebbing and flowing of the Tide, we are moft comfortably cijcumftanced ; for, generally fpeaking, we can tell to wonderful V i \ . >■ * .1 ( ”7 ) ful exa£lnefs, when it will flow, and when it will ebb; when we may expert high Tides, and when we may hope to have low ones. But I believe no Man has been able to tell precifely the Height that fome fpring Tides may rife to, nor the Height and Power of the Winds when united with them. In this Cafe, therefore, you muft paint to your Imagination, the moil: powerful Effffts of them you can poflibly conceive, and defign your Work after fuch firm and fubftantial Methods, that it may be able to with-Hand their utmoH united force: And in order to exert our belt and utmofi: Endeavours, let us begin with a fmall Beacon, or Light— houfe, before we attempt the more weighty Matters intended- SECT. I. Concerning the building of a Beacon, or Light Houfe in the Sea,. Prop. XI.r | ^ 0 build a fubflantial Stone, and Lime Beacon, or Light Houfe of 2 0 Feet Diameter in the Sea, the dead low Water being about eight Feet deep; and fpring Tides fome times rife ten Feet more- METHODS laid down inVlater XLIII. XLIV. XLV. and XLVI. Scale 12 Feet to i Inch. Plate XLIII. Fig. t. Furnifhes you with an Idea of the Land-front of the lower Part of the .Light-houfe, Handing, as it were,* upon the Coffer, Huffed and fioored as formefly directed. Wherein; note, A. Bottom of the Water. B. Low-water mark. C. High-water mark. Fig. 2. Shews the Ground-plan of the principal! Timber of one half of the Coffer, exclufi ve of the Grating. Fig. 3, Reprefents the Surface of the other half of the Coffer, floored with the Cut-Hones, and cramped as before directed; and alfo, the; Plan of the lower half of the Light-houfe, which is to be wrought folid with cut and large fcabbelcd Stones, except the Stair-cafe. Plate XLIV. Fig. 1 and 2, (Scale 12 Feet to 1 Inch.) Shews the principal Timber and the Grating. In which obferve, that all the principal;:( j28 ) principal Timbers are to lie exa&ly over one another, and fo are all the extreme Timbers that furround them. Fig. i. Reprefents half of the id Courfe, and Fig. 2. half of the 2d Courfe, which together make the Grating or Bottom two Feet thick, in both of which, the principal, or diagonal Beams, are to extend 60 Feet $ Indies; four Inches being allowed for the fet-off, that is to be on the 2d Courfe: And as you cannot get Timber of 60 Feet long, you are to take particular care that the Timber of the 2d Courfe, ufljfll break Joints with the Timber of the 1 ft Courfe, and that they be both firmly fplicedand bolted together, to prevent their wrecking, fwagging or diflocating by any Accident or Mifmanagement in the launching of the Coffer. And befides thefe Iron Bolts, there muff be an Abundance of Oak Keys, both through the principal and through all the outward Timbers. By Oak Keys, I mean, that you lliould get a competent Number of Pieces of Oak tried up, of about 2 Feet long, 9 Inches broad and 4 thick, each. The Mortices for them, muft be made quite through each Piece, and exadlly anfwerabie to each other; and thefe Keys muft be drove into the Mortices, and pinned with Oak Trundles of about full Inch Diameter, fo as both the under and upper Courfes of all thefe principal and outward Timbers, may be firmly united together. And you fee that between thefe outward Timbers in each Courfe, there is to be a Vacancy of eight Inches, and in this Vacancy the upright Piles are . to ftand, which Vacancy, and the Manner of framing the diagonal and outward Timbers together, you may fee laid down in Fig. 3. (Scale 2 Feet to 1 Inch) and when thefe two Couries are compleatly united together, you are then to put on your angular Plates on the upper Courfe, and in Cafe you have no bea-braces, then each of thefe Plates are to have three Wings, two of them are to encompafs the Angle, and the third is to go underneath the End of the diagonal Piece, with two Bolts through each of thole Pieces, as you fee marked out in dotted Lines. The Neck that proceeds from thefe three‘Wings muft be of about the Subftance of full three Inch fquare Iron at the leaft, with either a Hole, or a Jving, to receive the buoy Ropes, as has been formerly directed; and st i 4 \ t \ i j i i ,:' j! i, ! I1!.]' ir 1 h i trj I Hi U Mil Hi! 1 m 1 liHlIllflit |ii 1 • . ;; | ! ' 1 ,11 > j Mm i, • ;||i ii!ll!!. 1111 i 11 i I; 1 j. li.t:! il 1! [i S ll I l . .k ill, t;::! ; Lliiiuil ■JiJl.ll ymmiwwumH mirror intniiminumtiiHninnitniranniiwi ilWBnl ( «9 ) and if you have Sea-braces, you will find them defcribed in their proper Place. Plate XLV. Fig. i. Scale 5 Feet to 1 Inch. Is the Sedlion of one garter of the Coffer, as if it was compleatly ftulTed, with the cut Stone Floor, and the four firfb Courfes of the Light-houfe built upon it. Fig. 2. (fame Scale) is the Plan of the upper Timbers of that Quarter, with the Brace-bars and other Iron Work. Fig. 3. Scale 2 Feet to r Inch. Shews you how the three Rows of Piles are united together. You fee that the Hull is compofed of three Piles or Planks 'of eight Inches thick each, and their Breadth at Dil-cretion. They are all to be tongued and grooved as formerly directed, and firmly pinned and bolted; the three Piles taken together, making, as it v/ere, one folid Thicknefs, of which the middle Row' (aS you may fee by the Sedlion of the Hull, Fig. 1.) is; the Tennon, and goes down two Feet between the outward Timbers, which are the Bafe of the Hull; through each of which outward and inward Pieces, and through each of the upright Piles, there are to be Oak Trundles drove, of an Inch and a half Diameter. In this Fig. .3. you alfo fee the comer Pods, into which the diagonal Pieces are to be double dovetailed; and alfo, the Tongues of the two next upright Piles are to be let into Grooves, which you are to prepare for them therein, and fo are the Ends or Tennons of the infide horizontal Piles alfo. Thefe corner Polls are; to be made .of Oak, in two Parts', which are to be firmly keyed and bolted together, after you have made all the Grooves and Dovetails belonging to them; and you mull recoiled! the Vacancy left between the out-fide Timbers in the lad Plate, and make two Tennons in the Foot of this Oak Poll, or double Poft, exactly to fit and Hand in the-Vacancies, one on each Side, to fit the dovetail of the diagonal.Beam, in which two Places they are to Band, as it were, on two Legs allride the diagonal Beam, wherein they are to be fecurely bolted. And I mud repeat, you are not to forget, that in the Middle cf the Interfection of all the upright and level Piles in the Hull, there are to be Inch and half Oak T rundies drove tight through them, and wedged in the infide. Every Pile of the outfide is to be dovetailed at the Angles, like fo many Belts,: S to( *3° > to confine the whole Hull together, and you fee how the Iron work is to be applied thereto; but you muft alfo ftridtly obferve, that all the.Tongues and Grooves, both in the upright and level Piles, are to be done after a Workman-dike Manner, fo that the fineft Particlfe of the Sand, or even the Lime-water, may not be fucked out through them by the Waves. Indeed the Joints in the Bottom may be an Inch wide, becaufe when it is launched, it will let the Water into it, which will help to fink it, and the finer Particles of the fluffing will foon fill them all up, of which you muft here allow an extraordinary Proportion, and the Bank will fecure them all. Plate XLVI. Fig. i. Scale 12 Feet 1 Inch. Reprefents the Se£tion of the whole Coffer, as if it were fluffed and floored with Cut-ftones; and the Section of the lower Part of the Light-houfe, as if it were Handing upon it. Wherein note, A. The Bottom of the Water. B. Low-water mark. C. High-water. D. The firft Floor of the Light-houfe. E. Part of the fecond Floor. F. Well-hole of the Stairs; and G. The Bank to be raifed at Diicretion; but ftridtly obferving not to let any Stone exceed a Handful in your banking: Becaufe, a large Stone is to the W7aves, as a large Tree is to the Wind, which will give great Oppofition to it, when at the fame Time it will pafs gently over diminutive Shrubs; which is evident by the Breakers on the Strand. Befides, large Stones make large Cavities, and large Cavities contain large Quantities of Water, and lkrge Quantities of Water operate much more powerfully than fmall ones, which I fha’ll demonftrate hereafter. Fig. 2. (by the fame Scale) Shews you the Plan of the upper Timbers of the Coffer, the Plan of the Stairs, and the firft Floor of the Light-houfe, with the circular Bar that is to be let into that Courfe. Fig. 3. Reprefents the Platform or Surface of one half of the Coffer, fluffed and floored with the Cut-ftone; and the eight llrong Lines reprefent the Cramps, which muft be made of 1 \ Inch fquare Bar, and funk fomething more than their full Depth into .the Stones, fo that the melted Lead will entirely cover them, and when they are eaten with ruft, they are eafily replaced, or more added if neceffary* Fig. 4. (Scale 2 Feet 1 Inch.) Shews you the Method« i i to % , ^ \ i( r3I ) Method of cramping the Hull and the Cut-done together, viz, The fquare c. goes through the three Piles or eight Inch Planks, with a Screw-nut on the indde. The upright of c. has a fquare Hole in the upper End of it; and the End of the Cramp, d. is to take hold of that Hole, which you are to thrud into it after you have cut or funk the Channel acrofs the Heads of the Piles, or Hull, and the cut Stone, which you may more clearly perceive by Fig. 5* (Scale % Feet to i Inch) Wherein note, that c. fliews the Hole, and d. the End of the Cramp that goes into it; but if it iliould happen, that fuch a Building was to be erected in any Place greatly expofed to dormy Flood-tides, efpecially off the Atlantic Ocean, I particularly advife, that you may add eight projecting Steps in like Manner, and in the dead of thofe three; and then the naked Body of the Light-houfe will dand on the Summit of the . eight Steps, which are jud at the High-water mark, which will put the Light-houfe quite out of the Power of the Waves, as you fee it marked out at H. And you may alfo extend the five principal, or diagonal Sills (in Plate XLI1I. Fig. 2.) fix Feet toward the Sea, and thereon fix your five Sea-braces, as in Plate XL VI. Fig. 1. Letter I. and on the Ends thereof, you may fecurely fix the fire hauling Rings, at the End of each of the five Sills. In Cafe you are required to erect a more fubdantial Light-houfe, fuppofe of 40 Feet Diameter, the Coffers mud at lead extend 1 20 Feet, and be made in two or four Teparate Parts, jud as the Timber, and other Circumdances, may bed anfwer your Defign; but in this Cafe, you may fet it upon eight Steps ^aiMtibove mentioned, each of which is an Arch in itfeif, and \ of the Length of each Stone will be tied in covered and fecured with the next Ccurfe that is over it, and fo the Waves will not have any Power to dtfturb them in the lead Degree. Acid in Cafe you diould think it neceiiary to fecure the Coffer or Cofdrs more effectually, you may environ and fecure them with douhie or fingle Guard-coffers; but if you do them in that Maimer, yen are to omit the ^Sea-braces of the inner Coffers, thli they may be funk as clofc to each other as pofFibiVyoa can; and let the Sea-braces be fixed to the Guard-coders, as before directed, in Fig. r. S 2 Letter( J32 ) Letter I. Obferve alfo, that in fluffing the Coffers in the Sea, you mull be much more liberal in the Proportion of Lime, than what we concluded upon for frefh Water-works, becaufe it will be in much more danger of being both wafled and Weakened; therefore, if you can procure Lime at a moderate Price, beftow it bountifully on fuch Work as thefe; for it is the Lime alone, that creates tire Petrification, and by all Means, that ought to be promoted. And if I have been too penurious in proportioning that expen five Article, let your own Difcretion, tempered with a little experimental Knowledge, condudl you therein I am confident, and I hope it has appeared evident, that this petrifying Quality is mofl affuredly one among numerous other mofl ufeful Properties, peculiar to Lime-llone; but how this petrifying Quality is to be heightened or haftened in frefh and fait Water, that indeed, is not within my fcanty Province to determine; therefore, I mofl humbly beg leave to recommend it to the fludy of curious philofophical Gentlemen, acquainted with the Qualities and Operations of Compounds, as I prefume there is a great Probability, that thefe my poor Gleanings may be thereby, brought to Maturity, and that by an induftrious Cultivation thereof, they may be rendered produdtive of Utility in Matters of fuch exceeding great Moment to the Public in general. There are many other Things necefiary to mention, but you will find them difperfed through the following Pages. • > ; \ / S E C T. II. Concerning the luilding of a Stone Pier in the Sea. Prop. XI IT | O build a fingle Pier-head of Cut-fone in the Sea, JL the dead low heater at neap Tides being 20 Feet deep, and high fpring Tides rifng 20 Feet more. Previous to our forming thefe or the like defigns, vre muft con-fider, that the Tides and the Winds have very powerful Effects, eipecially when united. Let us therefore, endeavour to find out fome certain and general Fades for this Purpofe; in order to which, it 1 w ■ry y jfw m if- f_ yl *•' y* * /• V . *' B / y,,/ * * '( 133 ) it may perhaps, be neceflary to obferve, that one cubical Foot of Stone, upon an Average, may be fuppofed to weigh three cubical Feet of Water; but Stone being more ponderous, itwillconfe-quently be. the more powerful in its Oppofition, and the fitter for our Purpofe. Let us therefore confider, as for inftance: In a ftilly quiet Lake, you mull; admit that the whole Weight of the Water, refts and Hands upon its own Bafis, that is, the Bottom of the Lake; and the Bank, or whatever the Inclofure of it is, fuftains very little Preflure by that Water. Let us now fuppofe, that Part of this Lake’is' inclofed with a perpendicular Line of 20 Feet high; which is the Pleight here given for the Tide. See Plate XLVJL Scale 16 Feet to 1 Inch, which Line is feprefented in Fig. 1. by the Line, a. b. Now if you were required to form a Brace, or rather a Stone Buttrefs,. to (Lengthen, and give that Line fufficient Power to keep its perpendicular Situation, fo as to be able to fupport itfelf and to fuftain the PrelTure of that Water, to the Extent and Height of twenty Feet, you mull; lay down another Line of the fame Length horizontally, and in right Angles with it, as, a. c. and then draw the hypothenufe, or diagonal Line, b. c. which diagonal Line, b. c. defcribes the Bounds and Power of a Stone Buttrefs, which will be abundantly fufficient to withffand the Preflure of this. Water, or at leaf; equivalent to it; which you may prove thus. Multiply, a. b. by itfelf, the Product will be 400, and a. c. by itfelf, the Product will be ,400 more, add thefe two together, and they will be 800; then take off your diagonal Line, b. c. and by your Scale, you will find it near 28 Feet 4 Inches;, and multiply that by itfelf alfo, and it will be equal to the Products of a. b. and a. c. taken together,. infignificant Fractions excepted; whence I think it is evident, that the Power of the Line, b. c. is equal to the Powers of the Lines, a. b. and a. c. and confequently ddcri^bes the Buttrefs required for a Hill dead Water. But now comes on the main Thing;. We are not to encounter with a Hill dead Water, but with the Tide, which is liable at all Times to join in Conjunction with moft powerful ftormy Winds; but Hill, fuppofing that they do not exceed our^wren Height of 2o Feet, (yet what Strength or Power thefe Winds and Tides may acquire( .134 ) acquire when united, is not to be eafily determined) but as I told you before, you muft form in your own Mind, the moft powerful Effefts of them imaginable, and thence draw your Conclufions, whereon you muff form your Defigns; fo that your Work may be lb fubftantial, as to with (land their utmoft united Forces; and always obferving, in Cafe of any doubt, to keep on the fure Side, throughout the whole Progrefs of your Works: In order to which, let us return and reconfider the Power which appeared fo adequate to the Preffure of 20 Feet high, and 20 Feet broad offtill Water. From b. and c. draw two other fuch Lines, which will meet together in the right Angle, d. which will augment our Figure, and thereby produce an exadl Cube of 20 Feet, which of Stone, or our Stuffing, upon an Average, would weigh 464 Tons, one half thereof, being 232 Tons, hath already appeared to be adequate to the Preflure of the Plain, a. b. which is equal to, 20 Feet fquare^ the other half of this Cube, being 232 Tons more, makes up a Power, which will certainly be fufficient to fuftain the utmoft Force of the Tide «nd Wind, a&ing together on the Side of the Cube, a. b. It is evident, that there cannot be any Rule found out, to determine with Precifion, the Strength and Powers of the Tides and Winds united. Let us therefore, at prefent, endeavour to ex-ercile our Reafon on the following experimental Suppofttion, viz. Let a Coffer ot 20 Feet Cube, the given Height of the Tide be Tirade, fluffed and floored after the Manner herein before, or after directed, and lodged upon any hard level Ground, on the Strand at Low-water mark, the Wind and Tide coming upon this Cube in any Direction, but fuppofe from the point, e. I prefume, that this Coffer will be able to fuftain the utmoft Power and Force of that Wind and H ide, for. as long a Time as Fir Timber being fp ex-pofed could be expected to laft; blit in the prefent Cafe, I conclude, however, that this cubical Proportion, would be too fcanty for our Purpofe, becaufe'if the Wind and Tide attack this Cube obliquely, as from the point ff theyTgain a great Advantage of the Cube, for they will have the Line, b. c. to difcharge their united lowers upon: And although the point whence the Tide flows may be determined, yetC *35 ) yet the Wind is variable, whence it is evident, that you muff not defign your Pier upon the cubical, but on the diagonal Proportion. Therefore lay down the Line, b. c. from a. to g. and the Line b. d. is to be extended to h. then draw the Line, h. g, which will augment our Dimenfions to about 28 Feet long, and 20 Feet fquare, and will contain about 11200 Feet folid, at 130 Pounds to the Foot, will contain 650 Tons weight. And fo your Pier being defigned on this Proportion, every 20 Feet fquare of fuch a Pier, would have at leaft a weight of 650 Tons to oppofe the force of the Wind and Tide, that may a£l upon fo much of its front; which is a weight fo exceeding great, that I believe there is no confiderate Man, but what mull allow that this Proportion will be abundantly fufficient, but this fliall be more fully, demonllrated in its proper Place. Now on thefe Principles, let us proceed to defign, and confider the Conftrudlion of the Body of the Pier; that is, from the given Low-water, to the Surface, or Bottom of the Parapet. See Fig. 2. (by the fame Scale) whereby the given Heights are reprefented; and note, A. Is the Bed or Bottom of the Water, a. the Low-water mark, bi High-water mark. Divide a. b. into four equal Parts: One of thefe Parts is to be added to a. b. as a moderate Proportion for the Surge, which will then make the Height a. c. fee 25 Feet, for the Height of the Body of the Pier. Then (fee Fig. 3. by the fame Scale)-draw your Bafe Line, a. q. and interfedl it with your Center Line, g. e. take the Height, a. c. which is 2 5 Feet, and add 6 Inches to it for the #4. Joints of Mortar, and fet it off from e. to d. and thereon form the fquare, d. e. f. g. from f. tcT e. draw the Diagonal, £ e. which by your Scale, you will find to be near 36 Feet. This Diagonal may be looked on as a reafonable Bafe for the naked Body of the Pier, which you mull divide into two Parts, and lay them down from e. to h. and from e. to i. and £0 having the Bafe and Height determined, draw the parallel Line, f. e. You are alfo to confider, that this Bafe Line of the Body of the Pier, cannot begin at h. i. in the Execution of the Work, becaule the Hull of the Coffer muff rife three Feet above this dead Low- water( 736 ) 'water mark,; a. And. that the three projecting Courfes, on which the Body of the Pier is to Band, will take up three Feet more; and for thele Reafons you mud transfer h. i. to s. t. which is to be the naked Bafe of your Pier, and fubtra&ing 6 Feet out of h. 1. (= 25 Feet 6 Inches, the laft given Height) there will be 1 9 Feet 6 Inches remaining for the Height of the naked Body of the Pier. u. g. Which you muft divide into 6 = Parts, as at t. k. and take one of thefe Parts, and fet it off from k. to m. and do the like with the oppofite Side 1. 11. and this.gives you the true batter, or diminifhing of the Pier; by which Method, you are to cut the Bevil Moulds for the Stone-cutters, and the battering Plumbs.for the Setters, &c. and deducting 1. n. and m. k. from s. t. there will remain n.m, = 29 Pket 6 Inches for the Breadth of the Body of the Pier at the Top, juft under the firft Courfe of the Parapet, which to avoid Fradions (which are not neceffary here) we fhall call 30 Feet, and this furnifhes you with the principal Dimenfions of the naked Body of the Pier; that is to fay, the Bafe s. t. H36 Feet, the Height u. g. (you know was 19 Feet 6 Inches, but we fhall call it) 20 Feet, and n. m.. 30 Feet, and fo 36, 30 and 20, are the principal Proportions for the naked Body of the Pier, for .a. Flood-tide of 2oFeet,ex-clufive of the three projeding Courfes and the Parapet, and including the whole together. Remember, that one Foot long of this Pier (which you will find reprefented in Plate XLVIif. Fig. 1.) will contain 817 folid Feet, and: 20 Feet running Meafure of the fame = 16340 Feet, at 1 30 Pounds to the Foot, will be 948 Tons: And fo you fee that every 20 Feet long of the Pier, will have 948 m ons Weight to oppofe the Powrer of Wind and Tide, acting upon the front of that 20 Feet long.' And this I am fure will be abundantly . fufficient to oppofe them.; and this Calculation will alfo be iiiefui to you in making your Eftimates, . All thele Matters being luppofed to be clearly underftood, let us in the next Place, confider the^Proportions of the Coffers for the Body of the Pier. Draw the Line, x. y. parallel to r. q. take the extent £ t. and let it off from e.. to p: and from e. to o. dr.aw the Lines p. v. and o. w. and p. o. v. w. gives ;you the Extent of the Coffers for the'Pier. Then to proportion the Coffers for a imgle 4( *37 -; Strait-pier Head, divide s. u. into two = equal Parts, and lay down one of them, from.p. to r. and the other from o. to q. draw the Lines r. x. and q. y. and r. q. x. y. fhews you the Extent of the inner Coffers for this Pier Head, the Guard-coffers being referred to their proper Place. Then, to determine their Height, divide u. t. into 6 = equal Parts;’ one of thefe Parts, added to the given Height A. a. gives you x. z.'*= 23 Feet for the Hull or outward Height of thefe Coffers. Thus you may augment or diminifh the proportions of your Diagram, according as the various Circumfiances that may attend your Defign, may refpe&ively require. Now let us colle£l and lay down thefe principal, and the more minute Dimenfions in fomething of a regular order. Plate XLVIII. (Scale 16 Feet to 1 Inch.) Fig. 1. reprefents the Se6tion of the Pier compleat, and Handing as if it were eredled upon its Coffers (which extend three Cubes and a half of Low-water). Wherein note, A. Bottom or Bed of the Coffer. B. High-water. a. Is the Low-water mark. b. The Top of the Hull. c. Bafe of the naked Body of the Pier. d. The Bottom of the Parapet, or Top of the naked Body of the Pier. And, e. (which you fee alfo comprehends the Plinth and Cord) gives the Height of the Top of the Parapet, which together make 7 Feet or about \ of Flood-tide, which is a proportionable Height to keep off the Spray; which added to the five Feet before allowed for the Surge, makes 12 Feet above the given Height of a Spring-tide, which you may increafe or diminifh at Difcretion. Fig. 2. Exhibits the Sedtion of the Pier-head, Handing upon its Coffer (which extends four Cubes and a half) the Height of which you fee is the fame as above. The Superffrudture or fmali Building on the Pier-head, will be hereafter fully delineated along with the other Parts of the Work. Plate XLIX. (by the fame Scale) Fig. 1. Reprefents half of the firff Courfe of the Hull and Grating for the Coffer of the Pier-head. Fig. 2. The fecond Courfe of the fame. Fig. 3. The firH Courfe of one of the Coffers for the Pier. Fig. 4. The fecond Courfe of the fame, Fig. 5. and 6. Shew you * of the next Coffys for the; Pier; On all which I fhall only now remark, that all the principal Beams in both thefe Courfes, are to lie exadtly over one another, T I and( ’38 ) and to be keyed and bolted together, breaking Joints according as the different Length of your Timber will admit, as formerly di-re£led, on the laid Propofition. ' I have obferved above, that I am very little acquainted with marine Affairs, and for want of that Knowledge, 1 muft confefs that I am at an entire Lofs to determine,’ whether this Coffer for the Head of the Pier, had belt to be in one or in two feparate Parts. You fee the conjugate and tranfverfe Diameters are equal to about 90 by 76 Feet, which really is an enormous Size: And therefore I fliall not fully determine this Point; but I advife you, that after you are determined as to the Situation of the Pier, and confidered the various Circumftances relative to it, you may lay down thefe Draughts by a larger Scale, or make a model of the Coffer by a Scale of one Inch to a Foot, and thereon take the Opinion and Advice of fome eminent Ship-carpenter, and afk him this plain Queftion; Whether it is pradticable to launch and fettle fo large a Bulk in the Place deflined for it? And on his, or other Mens Opinions, you may determine this point. For this appears to me the foie Difficulty, that can in any Ways attend this whole Work; and yet I cannot help thinking, that if it be built in a convenient Place, and a proper Quay made for launching it, as before mentioned, that in one calm neap Tide it may be grounded in its Place, and then all your greatefl Difficulty will be over; but againft that critical Time, take the utmoft Precautions to have your Crafts ready loaded, and every Thing neceffary to crowd in your fluffing, to keep it down when it is grounded. But notwithflanding the Hurry you will at that Time be in, be fure that your fluffing be properly mixed together, for if they throw Stones in one Place, and Lime and Sand in another, the latter will indeed petrify, but the former cannot, which you may eafily accomplifh by the Precautions I have already given you concerning the fluffing. Your beft endeavours and thofe of your Workmen, are abfulutely neceflary at thefe critical Times, in working as the Tide anfwers, both Night and Day, at Night by the help and Dire6tion of your buoy Ropes, till you fill it to the upper Timber. UponN ( *39 ) Upon thefe and other Confederations, I have dcfigned this Coffer entire, as being by much the more eligible Way; on which you may further obferve, that part of this Coffer oppofite to A. is explained in the next Plate. The firft Courfe of B. C. and D. in Plate LI. The fecond Courfe of the fame in Plate LIT. And a Sedtion at E. F. Plate L1II. Alfo obferve, that in Cafe you think it neceffary to have Sea-braces (as was fully defcribed Plate XLVI. Fig. i. Letter I.) you are to extend the four principal or diagonal Pieces, that will be next to the Sea, ten Feet each, as at G. whence fpring the four Sea-braces'; and if you think all that will not be fully fufficient, you may alfo extend the Ends of the Middle-fills in like Manner, as you feevat FI. H. and let Braces fpring from them like wife. Plate L. Fig. A. (Scale z J?eet to i Inch') Fig. T. Shews the Plan of that principal Beam united to the PIull. Fig. 2. Shews the Sedtion of the fame. Fig. 3. Shews the Plan of the Middle Brace-beam, going through the Hull. Fig. 4. Sedlion of the *fame. Fig. 5. Plan of the upper Brace-bcam; and Fig. 6. Section of the fame, and the Manner of cramping the Hull and the Cut-done together. ' Plate LI. Fig. B. C. and D. (Scale 2 Feet to 1 Inch) Fig. B. (as in Plate XLIX.) Shews the fird Courfe of the Ground-work. Wherein note, a. Out-dde Timber of a Foot fquare.- b. A vacant Space of 9 Inches wide, left for theTennon or upright Piles to dand in. c. Another Timber of a Foot fquare. d. The Beam into which the Ends of the fird Courfe of the Grating is to be let in by a running Mortice; but I believe it might anfwer full as well, and be much more expeditious, and fave a great deal of Timber, by fpiking and pinning on four Inch Scantling, to make a Groove for them. And on fecond Thoughts^ I believe that (in Plate XLIX.) it would be advifable to do the fame with all the principal Timber in both Courfes of Fig. 1. and 2. Fig. C. Shews the Ground-wrork of the out-fide of the Coffer for the Pier. Wherein note, a. Outdde Beam. b. Vacancy for the 6 Inch upright Piles, and c. Infide Beam. Fig. D. Shews the inner Angle, a. Is the Beam. b. Vacancy; and c. Beam, Me. T 2 Plate( I4° ) Plate LII. Fig. B. C. D. (fame Scale) Shews the fecond Courfe of the Grating, and the Plan of the Hull compleat; but obferve, that all the corner Polls, viz. a. b. c. are to be made of Oak; and that the fix Polls E. are to be made of the fame in two feparate Parts, and bolted and keyed together, as was fully defcribed in Plate XLV. Fig. 3. with only this Difference; that the Thicknefs of that Hull was three Times 8 Inches, and this three Times 9 Inches. Plate LIII. Fig. E. F. (Scale 4 Feet to 1 Inch.) That you may clearly comprehend this Plate, turn back to Plate XLIX. and in Fig. 2. Obferve the dotted Line E. F. which you alfo fee here laid down by this Scale, delineating the compleat Section of that Part of the Coffer, with the Plan underneath it, and by your comparing it with Plate XLVill. Fig. 2. you may fully comprehend the Con-flrudlion of this Coffer, together with what I’ve already exhibited. However note, that H. is the Bottom of the Water, and reprefents alfo, "the Sill that extends to receive the Sea-braces, provided you have no Guard-coffers. I. The Bank, which you may extend at Difcretion. K. Is the dead Low-water mark; and L. thews the Height and Rake of the Sea-braces, which may be applied here, or referved for the Guard-coffers, and may either, be double or fingle, juft as the Situation, or other Circumllances may require: And here pleafe to obferve, that as you now know the Ufe and Method of making the Sea-braces, you may alfo occafionally introduce the like in flat-bottomed Coffers; but particularly, they may be of very great Advantage in (Lengthening, fuch as are made for Tongues, Quays or the like, either in the Sea or in Rivers. Plate LIV. (Scale 16 Feet to 1 Inch) Gives you the Plan and framing of all the upper Brace-beams, exclufive of the Iron-work, which you fee applied to the like Purpofes in Plate XLV. Fig. 2. Plate LV. (fame Scale) Reprefents thefe Coffers compleatly fluffed and floored with the Cut-flone, and cramped with Iron; in which remember, that every Cramp mufl extend to the fecond Courfe of Stone at the lead, and when this Work is fo far accom-plifhed, you may proceed with the reft of the Coffers of the Pier, and leave the Coffers of the Pier-head in this fecure Condition, during« I 4 / * 'V r\ \ * (f v> > X *t« . * «* "V V- V — < , yr '•■ %' V *>..• -VW*-- •»* <4tv»'• t * . V. / % A % f 9 \ \ » ♦ 9 V J. /. ;i-v .* \ ;V •cV' » - • * ^r \ ( Hl ) during Pieafure. Obferving alfo, that after the fame Methods of Conftrudtion, you may augment or diminifh the Size, Shape of Strength of other Coffers, proportionable to any other defign or purpofe according as their various Circumftances may require, or as your own Reafon may diredb Plate LVJ. (fame Scale) Reprefents the Plan of the fourth Courfe of the Pier-head, built on the Platform, with the Timbers that are to be framed together, and Chain-barred as formerly diredled; and the like Timbers are to be repeated at about High-water mark: And obferve, that the Coffer which you fee left in the' Stone-work of the Body of the Pier, G. is to be filled with Ruffing,, ’till you come to the Platform. It may alio be necefiary for you to obferve, that lo much a& you here fee drawn of this Pier-head, is drawn as if the whole was to be wrought with Blocks of Cut-ftone; yet, I do not by any Means recommend that as abfolutely necefiary, for the Remainder of the Body of the Pier, except you have fuch Stones very cheap ;• but by all Means, let the Headers, Stretchers and Tail-bonds, efpecially in the Side next to the Sea, be done with fuch Cut-ftone as we have hitherto recommended; but the interior Work will anfwer effedtually, if it be built with rough Stones carefully laid in fwimming Beds of good Mortar and grouted. I know there have been very eminent Gentlemen, who warmly recommended a peculiar Method of cutting the Stones for the out-fide Work after this Manner, viz. To double Dovetail all the Headers, and to fit the Stretchers to fall in between them, and fo lock them into one another; but I do not advife you to follow that Method, becaufe it will be tedious, troublefome and immenlely expenfive, and of little or no Advantage to the Duration of the Work, for this material Reafon: /. e. The Wind, and the flux and reflux of the Tide, do operate and principally exert their Power on the Foundation of the Pier and Pier-head, and not on the Body of it, efpecially, if it is built in (hallow Water. On which I fhall give you a full Demonffration in tjie next Se&ion; nor do 1 think it abfolutely necefiary for you to finifh the outfiae of the Work neither, in plain Athlers or in ruftic Work, except you'( I4S ) you do it for the Neatnefs of it: It may very well fuffice, to cut the Stones fquare in the ufual Way in Foot Courfes, and in every Courfe to make a two Inch fet off, which with the help of the battering Plumb, will preferve the diminifhing of the Pier, and keep it out of winding, and though it will look a little rough to the Eye, yet it will be very effedtuah Plate LVIl. (Scale 8 Feet to i Inch) Furnifhes you With a Plan of the Syperftrudture of the Pier-head, furrounded with the parapet Wall, on the level of the third Step above the naked Body of the Pier, (which was reprefented in Plate XLVIII. Fig. 2.) Wherein note, a. Store-room. b. Stair-cafe. c. A neceflary under the fame. d. .Sewer to be carried out under the Cut-Hone Floor, e. Bed-chamber for the Lamp-lighter, &c. f. For his Provifion, Coals, &c. G. The three Steps before-mentioned, the firft of which terminates the Parapet on the Rear of the Pier. Plate LVIII. (Scale 8 Feet to 1 Inch.) Fig. r. Plan of the Stairs, Oil-clofet and the Balcony. Fig. 2. Section of the Hall and Oil— clofet. Fig. 3. Section of the Store-room, and half of the Door into the Balcony, the Parapet being omitted. Plate LIX. Fig. 1 and 2. (Scale 4 Feet to 1 Inch) Exhibits the Plan and Elevation of the Balcony illuminated. Fig. 3. (Scale 1 Foot to 1 Inch) Is the Sedtion of one of the Globes, which mufl be made of very thick white Glafs; and though I do not take upon me to determine, whether Semi-globes, or common fquare Lamps, will prove moft commodious for your particular Purpofe, yet I wall venture to fay, that any of them will be preferable to Coal-fireS, for many fubftantial Reafons, that will quickly occur on a little Confideration; but as I have mentioned Semi-globes, I {hall give you my Opinion of them, and whence I conceived my Notion of one fort of them. For fome particular Ufes I had different fets of Moulds made of caft Brafs, fet in Frames of Iron; and at a Glafs-Houfe in Southwark, I had them filled with the hot Metal; and they took the form, and anfwered my Purpofe effedlually. Hence I conclude, that you may eafily get concave and convex Moulds made, that will admit of the Metal to be three Inches thick at the in the Semi-globe; and the convex Mould is to be prefled down***■' \ % \ * t w « 3 I 'f •r - ftlrl.y ->*»«* ( A F.4« > € i » i » i * ✓ it j s ( r43 ) down with a Leaver into ft: See Fig. 4. (Scale 1 Foot to 1 Inch.) Shews you the Section of this Semi-globe; and they may all be fet in Iron Frames, leaving what room you pleafe for your Lamp to ftand in behind them; which I think may be very fmall, for even the light of a fmall Wax-candle placed in the Center of it, cannot fail ol producing, to all appearance, a very luminous Ball of Fire, whofe powerful Rays mud needs be very confpicuous, efpecially if the Glafs is clear and well polifhed. And what then mull the whole Illumination be with nine fuch Semi-globes, extending near 12 Feet and 5 Feet high, all as if it Were one Body of Fire, that will require very little Care or Expence to fupport it, nor the leaft danger of its difappearing through negledl, and thus you may, if you pleafe, illuminate both your Light-houfe and this Pier-head, and make other ufeful Improvements on thefe few Hints. Let us now confider the Operations of Winds and Tides. SECT. III. Obfervations on the Jeparate Operations and united Powers of IVinds and Fides, a Bing upon the Heads of ftrait and curved Piers; built in the ujual IP ay at or near Low-water mark, I HOPE we have fully confidered and determined on the Power of the Wind and Tide in general: Let us now in a more particular Manner, obferve their Operations upon the Head of a Pier, that is run out from the Shore in a direfl Line, and built on a Bed of fine Sand at Low-water mark as ufual. See Plate LX. In Plate LX. Fig. 1. Note, that a. Is the fpringing of the Pier from the Shore, b. Reprefents a. double Pier-head, which you may obferve is much ftronger than the former, c. The open Sea. d. The Harbour, e. The Current of the Flood-tide running by b. into d. And f. the Current running along the Shore to a. The Drifts of all thefe Currents are reprefented by Darts; by which you may obferve, that the Current f. finding itfelf oppofed by* the Pier, which directs and guides it to b. in order to fupply d. and during its Progress, it is prefled forward by that which comes in( *44 ) the like Manner behind it; and alfo meeting with frefli fupplies from the intermediate Currents, it thereby increafes its Power, and quickens its Velocity, in proportion to the Length it runs, till it meets with the Current e. on which a violent Conteft enfues, each Ariving for Superiority; but e. being much more powerful, foon obliges f. to yield, and prefles it feverely againfl: b. where they unite, and if fuch a Pier was built at the Mouth of a large Tide-river, and the Tide flows up for many Miles into the Country, the further it is to run the greater Quantities of Water wheels round it, and confequently, the greater will the Velocity be at the Pierhead, where it faps and preys on the Bed of Sand on which it is founded; and at the fame Time the Water carries every Thing with it, that its Power is able to conquer. The alarming Effedts of this may eafily be difcovered by Fig. 2. In this Fig. 2. g. reprefents the extreme Part of a Pier-head, built upon the Sand at h. which is Low-water mark. The fatal Effedts of the Current before-mentioned may be perceived by the Curve-line 1. which reprefents a great Cavity, worn away and carried off by the two Currents e. and f. from about the Extremities of b. In order to prevent this, and preferve the Pier-head, it has with fome been cuftomary in the like Cafes, to throw down large Stones round it, fuppoflng they would preferve it; but let us in the next Place, confider the powerful Effedts of the Wind and Tide adting In Conjundtion on the Stones and Pier-head, g. We need not enlarge on the ufual Swell of the Sea; but let us briefly refledt on the Power of an enraged Sea, agitated by a violent Storm; and fuppofe a Wave advancing from f. toward a. Fig. 1. where the Pier gives it a powerful Repulfe, and diredts its Courfe to b. and fo advancing along the Pier, a fecond Wave in like Manner pufhes forward the firft, and the third the fecond, &c. And as before the Power increafes progreffively, in proportion to the Length of the Pier; fo that by the Time the Current, which the Impetuofity of thefe Waves will promote, arrives at b. if in Time of Flood, it will there join with an increafe the Power of the Current, e. and after all, it may be very probable, that other Waves may prove £>uch more injurious to b. eyen than thefe. Let us? therefore,( H5 ) fuppofe the Wind blowing in a diredt Line, as from i to b. in Fig. i. or from k. to g. in Fig. 2. and that a huge Wave advancing from k. to g. where the foaming Surge dafhing againft the Pier g. breaks by that powerful Obfaudtion, and then the Remains of it furioufly recoils, as it were to recruit itfelf, and is joined with the next Wave, and makes another Attack upon g. then recoils again, and fo on alternately. Now pleafe to obferve,. that thefe large Stones have (as I told you before) large Interfaces or Vacancies between and among them; and the larger the Stones are, the larger are thefe Vacancies, and, like a French-Drain, will freely admit the Water to pafs and repafs. Confider then, when the Wave makes the Attack, how powerfully it forces its Way through every one of the Vacancies; and, in the Repulfe, think what a mofl powerful Sudtion that Repulfe will create, and how it will agitate the fub-terraneous Water backward and forward, by the quick'Motions of thefe Waves; and you know that the main Drift and Operations of the Water naturally gravitate to the Bottom, and thereby break and rake it up inceflantly. Now recoiled! the tumultuous Velocity of the Currents, f. and e. operating (if in Time of Flood) at the fame Inftant, and together with thefe Waves, hurrying all the loofe Sand and didurbed Matters they are able to command along with them, until they have encreafed that Curve-line, 1. Then there will certainly be more of thefe large Stones thrown in;, but the Wind and Current operating as before, they will foon link that Bed of Sand to the Curve-line, m. which by this Time will begin to fap the Foundation of g. but that cannot be readily perceived, yet by a few Notes taken from the Sounding-board, it may eadly be difcovered, by obferving the Line m. by Degrees linking: down to the Line n. which will dill continue to advance O I # further and further under g. ’till at Length- it will totally deilroy and demolifh it, unlefs it foon meets-with a Rock or fome hard Ground; and if a fmgle curved Pier fhould happen thus to be erected, the Operations of the Tide and Wind, may perhaps, a£t nearly after the fame Manner as juft now defc'ribed; fo that I need not repeat them. Hence it is alfo evident, that the locking of U Headers( U6 ) Headers and Stretchers together, no, nor all the Chain-bars, Cramps or Ties you can make ule of in fuch a Pier-head, cannot preferve it after any confiderable Part of the Bed whereon it {lands is fapped and carried away from under it; which is a Truth fo felf evident, that I need not enlarge on it. Therefore, I recommend it to you to remember this, and to examine your Ground well before you attempt to lay a Foundation on it, efpecially at or near Low-water mark; but let us obferve the Operations of Wind and Tide, on a Harbour inclofed with two Piers. See Fig. 3. This Fig. 3. Exhibits the Plan of an Harbour inclofed with two Piers; and let us fuppofe, the Tide flowing from the South along the Shore, as from o. to G. and on approaching the Pier, is there-* by repulfed and conduced round to q. and w. and in its Courfe, the fmall Dart at r. infinuates, that only a fmall Quantity of the Tide comes into the Harbour, juft fo much as is barely iufBcient to keep the Water therein on a level with the ambient Water. The fmall Dart, t. fhews the Current of the Ebb-tide, and if the Current, p. had Liberty to exert its Power, it would be repulfed by an Arch that could not yield to its greateft Forces; but there you fee it joins with o. and continues its Courfe to q. and w. and the Current s. which feems to run diredlly to the Pier-head at t. is there alfo diverted and conducted to w. and q. but if we fuppofe the Flood tide coming from South Weft, as from u. it will then pafs gently by the Heads of the two Piers, leaving a fmall Quantity to keep the Water on a level as before; and the whole Current of that Tide.pafles alfo on to w. and q. without even attempting any injury to either of the Heads. Befides thefe Advantages, a Harbour of this kind may probably afford an excellent flicker for fmall Veflels to the Northward of the Harbour, provided the direct Lines of thefe Piers extend any confiderable Way into the Sea; whence I ,think it is evident,, that fuch a Harbour, if effectually executed, and in a proper Situation, may be reafonably fuppofed to anfwer all the Purpoles for which it was defigned. I think, therefore, we may now endeavour on the Plan before us, to form and lay down principal Rules to deftgn a Plan, for a Harbour of the largeft Magnitude; but it may not be- improper to take into our Obfer- vations,( r47 ) vations, that if a Ship is making her Way from the foutherly Quarter, as from s. or u. to H. in a ftrong Flood-tide and violent Storm, it may be in great Danger of running foul upon the northerly Pier-head ; and this you muft confider, and take particular Care to guard againft. SECT. IV. Concerning the ConftruElion of commodious Harbours of the large ft Magnitude in the Sea\ with Ohfervations on the Operations of the TVaves on the Pier-head. Fig. 4. And alfo, a concife Summary of the Principles on which th£fe Propoftions are founded. BEFORE we can proceed in forming any Delign of a large and commodious Harbour, inclofed with two Piers, as in Plate LX Fig. 3. I think it neceflary to find out fome one Dimen-fion, from which we may derive a Probability of giving due Proportion to the whole: And it is evident, that here alfo we muft be governed by the Depths of the high and low Water, which were already fettled in Plate XLVII. Fig. 2. but the Depth of the Low-water is here particularly to be regarded, becaufe deep Low-water will invite large Ships, and large Ships muft have a large Space to make their Tack, See Fig. 3. which is laid down by a Scale of j 00 Fathoms, or 600 Feet to 1 Inch. In this Fig. 3. you are to obferve, that A. muft be looked upon as your Model, by which you are to Proportion the whole; and here it is to reprefent the Depth of the dead Low-water, which was given at 20 Feet deep; therefore from the Point A. draw your perpendicular Line, and interfedt it with the Line B. C. take the Depth A. and multiply it by 100, and that will give you 20O0 Feet, for the Extent of the Line B. C. which you are to divide into ten equal Parts; then take five of thofe Parts, and fet them down from the Point A. to H. and there draw the Line D. E. The Interfedtion gives you the Center, from .whence defcribe the Semi-circle D. A. E. which is the outward curve Line bf both thefe Piers. Then fet in 72 Feet, or fix Fathoms, for the inner, U 2 or( 148 ) cr principal Coffers of the Pier, (which appeared by p. o. v. w. in Plate XLV1I. Fig. 3.) at D. and E. and thence defcribe the inner Arch, and there will remain 1856 Feet for the Cord thereof; and upon thefe two Curve-lines at A. you are to form the Mouth of the Harbour, and Heads of the two Piers. See Fig. 4. Fig. 4. (Scale 40 Feet to 1 Inch) Reprefents the principal Lines of a Se£tion of one of thofe Heads, taken parallel to the Line A. H. and may convey an Idea of one of thofe Heads, Handing upon the Coffers. Wherein note, that a. is the Bottom. 1. Low-water. c. High-water, d. Center of the Pier-head, e. Platform, (about 64 Feet broad). And you fee that all thefe Coffers together extend ten Cubes of A. (i. e. 10x20=200 Feet). The Letter f is the center Line, g, g. Extent of the two inner or principal Coffers of the Pier-head, which may be environed with flender tongued and grooved Piles, to preferve the Lime-water. g. h. Breadth of the Guard-coffers, which are alfo to be environed with very flout Guard-piles, (the Tongues and Grooves to be put on with Spikes and flout Oak Pins, or made out of the Solid) to be drove down by an Engine, between the Sea-braces, as deep as poflible, and then banked as before directed. /. Is the Lip of the Guard-coffer, and k. we fhall fup-pofe to be the Face or Front of the Pier-head. And having explained and confidered all thefe Proportions, let us proceed to form the Mouth of the Harbour* To find out the Centers of thefe Pier-heads: Divide the Line F. G. into eight equal Parts. Draw two Lines from the mid-dlemoft of thefe rarts, till they interfedt the inner Arch-Line, which gives you the Centers required; which is equal in Dif-tance to 500 Feet from Center to Center, or the fourth Part of F. G. (i. e. A. = 20 x 25 = 500 x 4 = 2000.) and each of thefe Centers are the fame as f in Fig. 4. Whence the Whole of the Coffers projedls 100 Feet, or five Cubes of A. from f. to A, on each Hand, leaving fifteen Times A. or 300 Feet, for the Mouth of the Harbour between the Coffers. Thus you have feen that the Depths of the Water laid down in Fig. 2. Plate XLVII. has prir^cipally governed the whole of thefe Defigns. The Height( *49 ) Height of the fpring Tide, a. b. direfted you to Proportion the Pier, and the Depth of the dead Low-water, a. A. enabled you to proportion the Extent of this Harbour; each of which, or any Part thereof, you may by the fame Rules, either augment or di-minifh, according as various Circumftances may require. Having obferved the Operations, and confidered the united Powers of Wind and Tide abting upon the Heads of ftrait and curved Piers; let us, in the next Place confider, that if a Ship is making her Way from s. or u. to H. in a ftrong Flood and violent Storm, fhe may perhaps, be in danger of running foul upon the oppofite Pier-head. ' To this Intent, let us ferioufly refle£t on what has palled, and attentively confider, whether fuch a Work as this would be able to fuftain fuch a violent Shock, as might happen from a large Veflel being precipitately forced againft it. I prefume it is quite out of our Province, to determine precifely, the Power of any fuch Weight ftriking againft either a direct or inclined Plain, fuch as I apprehend either the one or other of the Sides of thefe oftagonal Coffers may fitly be compared to; but let us much rather endeavour in a plain clear Manner to confider, whether we may reafonably hope that this Work (fuppofing it to be properly executed) would be able to withfiand fuch a powerful jfhock or not: And on this enquiry, we muft firft obferve, (fee Plate LX. Fig. 4.) that the Head of this Pier is fo remote, that even the feeble point of a Bowfprit, would perhaps, fcarcely reach to touch it, and therefore, the Coffers alone mud fuftain the fhock. Now it is.neceffary alfo to obferve, that thefe CofferH taken together, from h. to h. be 200 Feet Diameter, and 23 Feet high, as hitherto determined; and here .recoiled! the fubftantial Conftrubtion of the Coffers formerly laid down, how firmly they are braced, and made perfectly folid and compact with fubftantial and durable Materials; and that the Lip of the outward Hull, may perhaps, feem tp be the feebleft and moil expofed Part of it. Now, in order to reconfider this, turn back and look at Plate LV. You know how that was dire&ed to be done, and this is to be done after the fame Manner; and think, how firmly and fub- ftantiaily( *i* ) ftantially that Cut-ftone Platform will brace and ftrengthen the Lip of that Coffer. Confult your own Reafon, or that of any other judicious Perfon, on this plain Queftion, viz. Could any Ship by running foul on the Lip of thofe Coffers in any Diredtion, com-prefs the Stones of this Platform any clofer than they are here fuppofed to be laid? and if not; How can they yield or give Way tp it? But taking it in another light: There is no doubt, but that even fome Mariners will apprehend, that fuch a Coffer would be an infignificant Obftacle to a firft rate Man of War under full Sail; but it may be alfo neceflary for them to confider, that this Coffer (exclufive of the immenfe Weight of the Pier-head, and the lofty Beacon, or Light-houfe, that is to ftand upon it) would weigh upwards of fifty thoufand Tons, which we have found to be equal in Weight, to a folid Rock of Portland Stone of thirty-four Fathoms in Diameter, and near four Fathoms in Height; whence, perhaps, he or they may be able to form a clearer Judgment on the Effedts of fuch a Rock, lying directly in the Road of fuch a Ship under full Sail; and on the Decifion, you are to anfwer the Queftion propofed. We fhall in the next Place, make fome concife Obfer-vations on the Operations of the Waves on the Pier-head now before us. (Fig. 4.) The Depth from a. to b. being Feet. Let us confider a large Wave advancing from. b. towards the fuppofed Pier-head, k. in its Way, the lower Part of it only will meet with, and be retarded by the Obftacle, i. the upper Part of it, will break and difperfe on the Cut-ftone Platform, e. and being thus weakened, when the remains of it ftrikes againft k. it will make but a very feeble recoil during the Time of Low-water or young Flood. But let us fuppofe, a Wave advancing in a diredt Line from c. to k. it will not meet any Obftacle till it arrives at k. where its full Power can only ftrike on one point, and dilperfe circularly, which will partly diminifti its Power in recoiling, and the remaining Part of its recoiling Force, not meeting with lav Obftacle, will be quite fwallowed up in that Depth of Water. And alfo obferve, that Waves advancing through the intermediate Space, between b. and c. both their attack and recoil will operate entirely( *5* ) entirely on e. which will be, as if it were, a Stage of Cut-ftone of 64 Feet broad, prepared for them to aeft on. The Motions and Celerity of the Waves, have been fully examined by many eminent Gentlemen; feveral of whom have on very juft Grounds concluded, that the Motions of the Waves, even in a high Storm on the main Ocean, does not fenftbly agitate the Water to any conftderable Degree of Depth, from the Surface of the Caveties thereof; fome fay, not exceeding oue Fathom deep: And if fo, then generally fpeaking, the Water at a. will continue nearly in its natural tranquil State, and confequently, can neither difturb the Banking, nor fap the Foundation. Hence it is evident, that the utmoft united Powers of Wind and Tide, can neither injure nor moleft thefe Coffers, which is the principal Thing required. But before I prefume to introduce this moft important Propo-fition into Practice, I think it advifeable to fum up, and to lay before you in one View, the Principles upon which I have founded thefe 12 Propofitions, which I fhall reduce to the following fix concife Articles, in order to your forming a clear Conception of their Nature and Utility. I. That found hearty red Fir-timber, kept conftantly in Water, will be extremely durable; and the Iron Cramps eafily replaced if neceffary. II. That thefe fmall Stones, properly mixed with clean, {harp, fandy Gravel, in JVater, exclulive of Lime, and being clofely and fecurely confined together, will inftantly become firm and corn-pad, and confequently be a fubftantial Foundation for any Building whatever. III. That the Stuffing hitherto recommended, will moft affuredly turn to a real Petrification; and, that each of thefe Coffers will, in reafonable Time, contain one compact Subftance, equal to the Strength and Durablenefs of a hard and folid Rock, which will be of the fame fhape of the clear of the Coffers in which they were moulded; and will be poftefied of this remarkable Advantage, that the longer it ftands, the harder it will grow. IV. That( *52 ) IV. That thefe Kinds of Foundations, in the weightieft Works, may (generally lpeaking) be effectually accomplifhed, with fur-prizing Expedition, perhaps, by an ordinary Ship’s Crew, and at a trifling Expence (in Comparifon with other Methods) in any Country, throughout the greatefl: Part of the Univerfe; as there are, probably, but few Countries that do not afford fuch common Materials as are neceffary for thofe Purpofes. V. That thofe Kinds of Coffers may be proportioned to any moderate Depth of Water; and that Coffers of fifty Feet high, may, in mofi: relpeCls, be as readily conftrudled, and the Work as effectually executed in a frefh Water, or in a moderate Tide River, as in any other leffer Depth, the Proportions being duly confiderfcd. VI. That in any kind of Buildings that may hereby be erected in the Sea, it may alfo be obfervable, that if the Coffers were even made much flighter, yet, as they will be in a Manner quite beneath the Power of either Wind or Tide, they may be abundantly fuflicient to oppofe them both, and confequently, they can only operate on the Cut-ftone, which they cannot injure. I hope, therefore, that 1 may fafely conclude, that thefe are fure, quick and cheap Methods for compleating fuch Works, which are the three Things that I have endeavoured to accomplifli. With this View, therefore, and on thefe Principles, I fliall now venture to introduce this Propofition into practice, by laying before you, the Plan of a Harbour tor the Downs, in England; which you may apply or vary, according as other particular Circumftances may require, either in that Place or eliewhere. And obferve, that in this enfuing Defign, in the Place of Fig. 2. Plate XLVIIL you may (by a large Scale) draw the Section, Fig. 4. Plate LX. with a SuperffruCture proportionable to it; and lay down the oCtagonal Plan thereof, fo as to corroborate with the Plans of thefe curvedTiers in Fig. 3. and alfo in Plate LX1. The Heads of which, I have been obliged, by the fmallnefs of my Scale, to draw circular, and to omit all the Guard-Coffers; but I hope, all the other Parts and Proportions of thefe Methods, are fo clear and dift inctly laid down in them, and in the foregoing Plates, that I need ngt enlarge any further on them; and( J53 ) and obferve alfo, that the Height of the loutherly Pier in this following Defign, mufr perhaps, be of the. fame Dimenfions as formerly laid down, Plate XLVIIL Fig. i. But the Pleight of the North Pier, is entirely left to your own Difcretion, with many other Circumftances which after ftridtly examining the Coaft, you mud determine on, as the Refult of deliberate Confideration. S E C T. V. Concerning the ConJlruBion of a TTarlour for the Downs, projecting to 2,0 Feet Low-water, the highef Jpring Tides fuppofednot to exceed 20 Feet more. I HAVE told you that in June 1752, I went to Ramfgate, to confult Mr. Ettridge and Mr. Prefon, who were pleafed to favour me with a Copy of the Plan of their Harbour. During my Stay there with them,, and the Captain that brought th&m the Portland Stone, great Part of our Converfation turned on different Opinions, concerning a Harbour for the Dowjis; and as I then had an Opportunity of hearing many pertinent Remarks on the Subject, to fatisfy my Curiolity, I took a curfory View of the Shore thence to Dover; and I afterwards colledted feveral other Plans, Charts and other Remarks; and on my return Home, employed one of my Clerks to copy them, and reduce the whole into a concife little Book, which now lies before me, and which I have many Times ftudied with the greateft Afliduity, in hopes of ac-complifhing what I moft earneftly defired: And at Length, I com-pleated what I am alfo now about to lay before you, as the ultimate End of thefe Proportions; but obferve, that all the Materials which I collected, were not by any Means fufficient to determine me, efpecially as to the propereft Situation for it, becaule I had not any Borings, or corredt Soundings of high and low Water; I muff therefore, leave thefe Matters at your Door, but fhall give you a few neceflary Hints concerning the Situation in the Sequel. X Plate( *54- ) Plate LXI. (Scale ioo Fathoms or 600 Feet to 1 Inch.) This Plate exhibits the Plan of the Harbour, which I have de-figned according to the general Rules of Proportion, laid down in Plate LX. Fig. 3 and 4. And herein note, that A. is the Mouth in tweenty Feet deep of dead Low-water. B. The Bafon for the largeft Ships, extending 1856 Feet, or about one third of an Englijh Mile, in the clear of the principal Coffers as before, which in this, or the like Cafes, you may difpofe of after the following Manner: Out of this 1856 Feet, take the odd 56 Feet, and divide them into two equal Parts, and give one of thofe Parts to enlarge the Thoroughfare at the Rear of the Lots; then divide the 1800 Feet into 18 equal Parts, three of which (being 300 Feet) are to be the Depth of the Lots on each Side, and the remaining 1200 Feet are to be the Breadth of C. which is to be the Port or Haven for trading Veflels, (which is juft the Breadth of the River "Thames at FFejhninfter-bridge). D. Is the Port-head at the Cuftom-houfe Quay, which muft be fix Feet deep at the dead low Water, a. and b. Are two fmall Beacons, c. and d. Two Quays of 328 Feet long, and 70 Feet broad each. E. and F. are twenty Lots for Docks, each Lot feventy Feet Front, and 300 Feet deep. Then divide the 300 Feet into three equal Parts, of which you leave two on each Side for the Depth of thefe Lots, and one on each Side for G. and H. which reprefents the two principal Quays, each of which will be 1770 Feet long, and 100 Feet broad. Wherein alfo note, that e. and f. are Thoroughfares to the Rear, and 50 Feet broad each. g. and h. Twenty-four Lots for his Majefty’s Magazines, being 50 Feet Front, and 200 Feet deep each. i. and k. Thoroughfares of 40 Feet broad. L and m. Thirty Lots of 40 Feet Front, for public Stores and Weigh-houfes. n. and o. Thoroughfares of 30 Feet broad, p. and q. Thirty Lots for principal Merchants Companies, to ftore their Imports and Exports, till further Orders. I. A yard, wherein you are to make the Coffers, &c. and afterwards it is to be the Cuftom-houfe Quay, extending 1200 Feet long, and 300 Feet broad.~~r MU ■! IIill! f||i\ \ t 4 * * \ 0 * ( i55 ) broad. K. Public Stores and Weigh-houfes on the Ground-floor, and Cuftom-houfe and Exchange on the Second-floor, &c. I fhall now give you a few fhort Hints concerning your making a proper choice for the Situation of this Harbour. I told you above, that I had only taken a curfory View of the Coaft, and therefore, cannot be expedted to fix upon the Scite; but from filch poor remarks, as I have been enabled to make or procure, for many reafons I apprehend, that a little to the Northward of Deal, or fomewhere about JValmer, would be very proper for the purpofe. However, obferve, that I do not pretend to determine this Point, or to enter into any minute Circumftances concerning it; but I fhall juft briefly recommend two principal Guides to conduit you to a proper Situation. I. Firft fet out in a direit Line from the mofl pfromifing Place on the Shore, till you come to fix Feet deep at dead Low-water, and that determines the Scite of letter D. Then proceed in the fame Direction, till you come into twenty Feet deep of the like Water, which gives you letter A. and herein obferve, that the Extent of A. from D. is juft equal to 4396 Feet in the clear; but I prefume, that it would be infinitely better, if A. and D. were double nay, treble that diftance, from each other, for this very important Reafon, becaufe the Merchants of London would be better accommodated, with a convenient Number of Store-houfes, to preferve both their foreign and domeftic Commodities, according as their different Occafions might require, without giving the leaft delay to their Ships or Men; by which Means, this Port would not only prove a Place of Safety, but among numerous other Advantages, it would anfwer extremely well as a Mart or noted Place to carry on Trade with the whole World. For thefe, and many other weighty Reafons, I advife you not to be afraid of making the Diftance too extenfive between A. and D. for when the Bafon B. is finifhed, the Expence of carrying the Piers home to the Shore, will be very trifling in Comparifon with the yearly Value any eminent Merchant would put upon one of thofe Lots. II. I fhall now in the fecond Place, point out another Guide to conduit you to a proper Situation for this Port, which you will find X 2 to( i5« ) to be of fuch vad Confequence, that neither Time nor cod ought to be fpared to find out and procure it, if poffible; and that is a full command of pure frefli Water. I cannot certainly fay, whether or no the River Slower could be taken up, or even, a Part of it, conveyed to fome convenient Place for this Purpofe; but I have Reafon to believe that it may, or perhaps, fome other Rivulet may anfwer better; but be that as it will, I do mod earnedly advife you, to procure plenty of pure freffi Water, fufficient to keep up in the dried Seafon, a fpacious Refer-voir, contiguous to the Rear of K. or fomewhere to the Wedward of the Port; and from this Refervoir to carry two Conduits, one through the Middle of each Quay-wall, as it were from r. to s. and from t. to u. they mud be at the lead 4 Feet wide, and 7 Feet high in the clear, to be built with well chideled Stone, in daunch Cidern Work, as formerly diredted, each of thefe Conduits mud have a Sluice at the Refervoir, and another near to the Extremity of each Quay as at s. and u. into which common Sucking-pumps mud be fet at about every Ship’s Length, in Proportion to the fe-veral Depths of Water, with proper Air-pipes, &c. This I repeat, will be of fuch vad ufe, that no Money ffiould be fpared to procure it. I ffiall give you but one Indance on the whole: Suppofe a Sloop or Tender, ffiould come to this Port in great hade for Ammunition, or Provifion, die might fail up to the Magazines and be indantly loaded; and yet, at the fame Time, by the Labour of three or four Men,, this pure freffi Water can be pumped, and by Leather-tubes conveyed, even into the Water Hogfiieads in the Holds; and with all this ffie might fet out again, without paying any regard to the Tide, or lofing the lead Time imaginable by taking in her loading. I do not in the lead doubt, but that there will be fome political Objections made to this Defign; becaufe perhaps, this Port might at fome Times contain immenfe Value of Britijb Property, and in Time of War be liable to Hodilities. In order to obviate that Objection, you may on thefe Principles and Methods eredt two f’ubdantial Forts at L. and M. provided you find thofe two Scites of( F# ) of moderate Depths, by which I prefume, this Port may be fafely protected, and the Channel effectually guarded thereby. Plates LXII. and LXIII. furnifh you with the Scales, by which all the foregoing; Draughts were minutely laid down, except Fig. B in Plate LX. and Plate LXI. Thus have I, to the utmoft of my Capacity, at Length gone through the Defign I propofed, and which I have fo much at Heart; and if the Ends 1 had in View fhall be anfwered, and thefe Sheets may in any wife conduce to the national Welfare, and the Infhu&ion of young Students in Works of this Nature, I fhall be fo far from regretting the Labour I took in compofing, and the Expence I have been at in publifhing them, that I fhall fit down with all the Self-complacency that arifes from a Confcioufuefs of meaning well. FINIS, ERRATA. Page 76, line zz, for homely read home.-Page ioo, line 9, for a. fe. and c. I Plate 2® read e. f. g. and h. in Plate "8. jig. 2.-P. 1.35. 1. 33./or f. e. read f. k./ «. 4 ♦ / i * t # » \ \ i a \ •L r. % 4 -r % / \Pi. 5. inch /t 1 s . . . — 3 a i 1 \ L ■ mil \ ? h_ 11 * /In \ £ p . ! L I t 1 \ Qr \ a 9 L i _i. \ \ 1 J a L. / 5 6 ~7 / & o j JO / -r # 4 — I 'P — / Mi / i 27? -21 20 to 17 jflj 15 i4 12? 12 // to I # 7 H 5 4 3 2 1 | - i—j— 1 — [. - 1 j —i _ ! ! 1 1 ■3 f. i 7 j t r-—3 , j— 1 — j /» | ; ' • 1 1 l — i L_d j t tn y| k i ' .1. ~l- 1 \j 10 l i ■nl ■ t 1 •' _ ■Lj » 4 / % w*I ( / I ♦ % % % * & RETURN ENVIRONMENTAL DESIGN LIBRARY TQt» 210 Wurster Hall 642-4818 LOAN PERIOD 1 QUARTER 2 3 4 5 6 ALL BOOKS AAAY BE RECALLED AFTER 7 DAYS Return books early if they are not being used DUE AS STAMPED BELOW inter-library LOAN JUN 9 1978 FORM NO. DD 13, 60m, 6'76 UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CA 94720V U.C. BERKELEY LIBRARIES CD3MTL73LQ 3pSKsiSlii aLOc7ciS3S6S^9S-SSl #7«Ag^ ferca^^BEpj^gl fj5 c^€Mi85g!P5rfiK^' .<8^601^8 |j8Kp!5H cite: 1 MM£: rTv imM^rfSoC^K TOTCCr jgIS& □ssSli ■ b^Eb^I cKtr^fl SfXsS^Z «5P 3^*8 ■ <.<"goa a58f *^®C3H s« BP^GgiMji ipt amral-i! tZjmmmM LZ-C^^St eC3*3ESW: BW r~ ■»Mii^rciaEgwi cl ftgiKiK^m g^