/
REPORT
IN EEb'EUENCE TO THE
CANAL TO CONNECT TUE CHESAPEAKE AND OHIO CANAL
"WITH
THE CITY OF BALTIMORE,
liY
Colonel J. J.
It
CHIEF OF THE COIll'S OF TOrOCRAl'IIICAL ENGIXEEUS, IS S. A.,
18 3 8.
KEI'ItlNTED FOE TUE USE OF TUE EKGINEER DEPARTMENT, U. S. A.
WASHINGTON:
aOVKKNMENT T KIN TING OFFICE.
1 8 7 4.
LCiV^ríT
f.'.- O" LWAY tcrvHQ^Jiftjli
-. 0.0
Lififim.
Office of the Chief of Engineeríí,
WasliiníjtGn, D. C., Novcniber 17, 1874.
Sir : Tlie subject of the improvement and construction of water-lines of trans¬
port to the seaboard, which is largely attracting attention, and for which numerous
surveys are now being made by order of Congress, has given rise to frequent applica¬
tions to this Office for a report of the late Col. J. J. Abert, Chief of the Corps of
Topographical Engineers, made in 1838, in reference to tlie project of a canal to
connect the Chesapeake and Ohio Canal with the city of Baltimore, as especially
interesting for the manner in which he has presented and discussed the general ques¬
tion of the quantities of water consumed or expended by canals.
This report is not a public document, but was addressed to tlic governor of Maiy-
land, and is now out of print. I would suggest the propriety of reprinting it by the
Public Printer for the use of the Corps of Engineers.
Very respectfully, your obedient servant,
A. A. Humphreys,
Ltrir/adier-General and Chief of Idiif/ineers.
Hon. William AV. Belknap,
Secretary of War.
Approved :
By order of the Secretary of AVar:
II. T. Croshy',
Chief ClerL
November 20, 1871.
B E P o R T .
To Iiis Excellency T. "W. Veazey, Governor of the State of Maryland :
1. In conseq[nence of tlie application of yonr excellency, dated the 23d of April,
1838, to the honorable Secretary of War, I was directed to receive your instmétions,
and to carry them into effect.. These referred to a survey of a route for a canal to
connect the Chesapeake and Ohio Canal with the city of Baltimore, and will bo found
more particularly expressed in two of a series of resolutions passed by the legislature
of the State of Maryland in March, 1838, in the following words:
" Resolved, That the Maiyland Canal Company are entitled to no sxtbscription on
the part of this State, under the provisions of this act of the assembly, unless they
will agree to locate the canal from the Chesapeake and Ohio Canal to the city of Bal¬
timore by the most northern practicable route of the routes by the valleys of the
Monocacy and the Patapsco, or by a route diverging from the said Chesapeake and
Ohio Canal at the mouth of Seneca River, exclusively within the limits of this State,
provided such route be found practicable, with due supply of water.
" Resolved, That the governor be, and he is hereby, authorized to direct a survey
to be made of the aforesaid routes, so that the practicability of constructing the said
canal by either of the said routes may be ascertained at as early a period as possible,
and report the same to the next general assembly."
2. From the foregoing it will be perceived that the locality of the routes of the
canal is prescribed ; that, wliichever route should be adopted, it must be exclusively
within the limits of the State of Maryland ; and that it should be "practicable, with
due supply of water."
3. Several surveys having already been made in reference to the same object by
engineers of much reputation, the possibilities of the case had become determined, so
that my. attention was, in the outset, limited, and relieved from the vague action which
would have ensued of an unknown and unsurveyed region. These previous surveys
confined those possibilities to throe routes, usually known as—
First, the Westminster route ;
Seeond, the Linyanore route ;
Third, the Seneca route.
There is a fourth also, the route through the District of Columbia to Georgetown;
but as this is not " exclusively Avitliin the limits of the State of Maryland," it could
not bo made a subject of investigation, as it fell without tlie locality of operations
whicli the legislature had directed to bo observed.
4. Of the routes named, the first had been so ixnequivocally rejected by the
engineers who had preceded mo that I did not consider it deserving of a survey. The
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second liad also boon rojectod, from its presumed deficiency in water ; but as it was
the only i-outo connecting with tlio valley of the Brouocaoy tliat bad a bnro possibility
in its favor, and as the legislature evidently bad tliis valley in tbeir contemplation wbcn
tbe resolutions tpioted were passed, itappeai'ed to mo proper tbat itsbould bo surveyed.
It bas accordingly been dono.
5. The third is the route by the valley of the Seneca. Upon this, and this alone,
have the onginoci's who preceded mo diiTeml In opinion : one, Sir. Trimble, declaring
it to bo nderpuifely supplied with water ; the other two, Slessm Fisk and Hughes,
being eipially decided that the supply was insuilicient. It was this diflerence of opin¬
ion which gave rise to the legislative action authorirdng reneived surveys, and which
induced your excellency to designate meas a sort of umpire in the case, with authority
to make whatever additional investigations and surveys might lie considered necessary.
G. I will not deny that I felt the embanmsniont of my position. "With all of these
gentlomcu I had been for years on terms of the most friendly intercom-so. All pos¬
sessed great reputation. IJlr. Trimble, a distinguished gmdimto of the Slilitary Acad¬
emy, had hccn, for many yearn, superintending highly important railroad-operations,
pos.sessing and deserving the confidence of his employem. Mr. Fisk had been etjually
long on tlioso of canals, and was then, and had been for some time previous, the chief
engineer of the Chesapeake and Ohio Canal. Mr. Ilnghes, his associate, it was well
known, was a gentleman of scientific knowledge, having passed through the courses
of the ]i[ilitary Academy, of a vigorous and inquiring mind, and had been for many
years employed by the United States as a civil engineer, in which ca2)acity his reports,
plans, and estimates on various subjects connected witli his profession hoar ample tes-
tmiony of Iiis abilities. To agree with both sides was impossible ; to differ with some
one, therefore, must ho the inevitable result of an honest opinion.
7. On entexing upon the duty, it was soon found proper to extend the surveys
much more in detail than had been at first contemidated, as well to gather all facts of
importance hearing upon the question at issue as from the difficulty of accurately con¬
necting ours with the labors of our jxredecessors from the deficiency of permanent
marks. But I hope by this courso that all necessary matter has been collected, so tliat
the question will bo satisfactorily settled.
8. Your excellency was duly ajxprised in tbe outset tbat it would not be in my
power to give much pei-sonal attention to the surveys. These were, however, commit¬
ted to able hands: iMr. Thonuis J. Lee being at the head of one party ; and Mi*. J. P.
Ivirkwood, of the other. The intercourse between these gentlemen and myself has
boon frequent, personally and by letter, so that no benefit that could be derived from
my advice has been withheld.
9. Becurring to your excellency's letters and instnictions and to the resolutions
of the legislature, as well as to the general principle which goverra in all' canal-cases,
it will be seen tliat the jioint at issue is " the due supjily of water," and that this is in
fiiot the sole point upon wliidh I am i-equii-ed to report
10. It will involve a reasoning not only upon the general question of tlie quantity
of water consumed or expended by canals, upon which it is evident that- one might
indulge one's sdf in a long eœay, hut of matters.fiuniliar to the profesdon, ahmdy
7
treated witli gi-eat ability by engineers, and wbicb in consequence would leave me at
most only the subordinate duty of repeating in my own language tbat.wliicb has been
so much better said by others. To the professional man, tlierefore, I shall probably
say nothing either new or interesting, and were I writing a report for Hs pœusal only
I should probably limit myself to a few results and deductions ; but writing as I am
for the judgment of the le^lature, which is not professional, I shall of necessity be
forced into tlie discussion of details familiar to the profession, but not so to those for
whom I write. And to be the better appreciated by these, I shall endeavor to express
myself in that simple and plain language which, if it should not convince, will at
least be understood.
11. The water required for a canal ought to be sufficient to supply an expendi¬
ture on the following accótmts : •
First, Infill the carvü throxt^hovA its whole extmt;
Second, to com2Jensate for losses fi-om evaporatioix ;
Third, to compensate for losses from filtration and absorption;
Fourth, to compensate for losses from leakage at the lock-gates;
Fifth, for the uses of the locks, according to the demands of the trade upon the canal;
Sixth, and for the toaste arising from accidents and negligences.
12. I mean to treat of these several causes of expense of water as briefly as a
clear exposition of each will admit, and shall endeavor in tLat way to establish certain
general rules, which may be afterward easily applied by any one who has a knowl¬
edge of the rudiments of arithmetic, to the particular project under examination.
18. But, as accessory structures to canals, feeders and reservoirs have to be made,
some facts and reasonings in reference to losses of water in these, and of the means of
filling reservoirs, will likewise have to be submitted. •
14. First, the quantity required to fill the canal.—This of necessity depends iipon its
dimensions—^length, breadik, and depth—and is obtained by resolving thorn into the
cubic unit of water used in the calculation. The result is, however*, always below the
truth, because, while the process of filling is going on, losses from evaporation, absorp¬
tion, and filtration are taking place. In strictness, therefore, these should be taken
into account, particularly in cases in which, the supply not being abundant, it would
be dangerous, from the delusion probably consequent, to neglect any item of loss.
15. Second, losses frotn evaporation.—Much has been written on evaporation by
autliors as a pliilosophical question; but it is evident, on an examination of their exper¬
iments, tiiat tlie result obtained can form no good data for calculating losses of water
from a similar cause on canals. What just comparison can be made between tlio cir¬
cumstances of experimente in a laboratory and tlioao wliicli exist on a canal f—tlie one
exposed to all the changes of temperature in different parte of its surface, to conunotion
in ite waters, to continual variations of humidity in tho adjacent bed of air, and to
greater or less cun-ents of air passing over its surface. From all these the experiments
of most writers on the subject have been comparatively free, and of consequence their
results are not safe data in reasoning upon evaporation on canals. One can easily bo
satisfied of tiiis by referring to tlio article on "Evaporation" in Ilutton's Matiiematical
Dictionary, and by reducing to oritlunctical results tiip jiroportions which some havo
8
endeavored to establish between evaporation and rain, and the reverse. Idioso pro¬
portions, if true in nature, can bo so only in peculiar localities ; as, for instance. Dr.
Drownrigg, in his trcati.'r'e n[)on making salt, states the evaporation in some parts of
England at 73.8 inches during the months of i^fay, June, July, and August, and at 140
inches for the Avhole year! To Avhat conclusions woidd these facts lead ns wore avo to
ap[)ly them in the proportions given by authors betAveen e\'aporation and rain?
IG. Also, ]\[r. Dahon found that, from the current occasioned by merely raising a
aa'indow, the ca'aporation of his ox^ieriments in the room in Avhich they aa'ere made a\ais
increased 50 per cent. ! Surely, such results are not to be ap¡)lied to the condition of
Avater in a canal.
17. That settled proportions exist betAveen evaporation and rain is not Avhat I
mean to dispute ; but to determine these for an extensiA'C district of country requires
numerous and long-continued observations in many places, under circumstances
brought as nearly as possible to those AAdiich actually exist in a state of nature.
Proportions can, Avithout doubt, be correctly established betAveen the eA'aporation of a
laboratory and rain as it naturalh' and actually occtirs. Put, then, aa'hat are those pro¬
portions ? Jlerely such as exist in the eA'aporation_of a laboratory on the one side,
and rain in a state of nature on the otlier! Xoav,. for a canal aa'c aa-ant the eA-aporation
of a state of nature. That determined at salt-Avorks, aa'hero artificial heat is notarised,
but merely the evaporation from large and exposed vats by the air, is most probably
the nearest ap¡)roximation to aa'hat actually occurs on a canal, diflerences of climate
and temperature being- considered.
18. I luiA-e been furnished by my eidightened friend Dr. Harlan, of Philadelphia,
Avith some results .of CA'aporation in that city ; but these are liable to the objections
already stated. There is no parallelism of circumstances Avith those of a canal, and
therefore there can be no just application of results.
19. I am convinced that losses on this account on canals much exceed the labora¬
tory-rules by Avhich engineers have been governed, and that this has often been the
unexpected cause of disappointment in the quantity of Avater anticipated.
20. EA-aporations are much influenced by climate. That of England being gen¬
erally colder and more moist than the climate of France, evaporation in the latter
counti-y shoiild be greater than in England. In our country, particularly in the Mid¬
dle States, Ave have more hot, dry, clear, and Avindy Aveather than in France, Avhich
Avould justify the inference of a greater eA'aporation with us than in Europe. We liaA'e
also more rain in the course of the year ; that is, a greater quantity falls in fcAver rainy
days.
21. From the considerations heretofore given, I am disposed to consider the
greater part of these rates of eA'aporation as inapplicable to the condition of water in
a canal.
22. The celebrated engineer Gauthej', in his interesting work upon canals, appears
to rely in this question upon the experiments made by Mr. Cotte at Montmorency,
near Paris.
The method pursued in making the experiments is not given by Gauthey, but the
result is that the mean evaporation per year amounts to 41.575 inches ; and that, for
9
parts of a year, (vol. 1, 266,) the results were: for November, December, and Janu-
'ary, 1.338 inches per month; for March, September, and October, 3.189 inches pèr
month; and for the six remaining months, 5.315 inches per month. These Avere prob¬
ably the results of some one year, as they do not agree Avith the average per year
before stated. The same observer also found the rain to amount to 18.662 inches per
year; from which he concludes that evaporation is to rain abont as 20 to 9, or as 5
to 2.25.
23. Dr. Halley fixes the annual eA'aporaiion at London at 48 inches ; and, on an
ordinary summer-day, at tAvo-tenths of an inch, and the proportion between that and
rain as 5 to 3. The experiments of Dalton and Hoyle'make it abont 4.41 to 3.
24. By particular observations of the engineer M. Pinn, on evaporation during
the suspended navigation {chômage) on the Languedoc Canal, (And., p. 223,) he deter¬
mined that the partial depression, OAving to evaporation, Avas tAVO-fifths of the total
depression of the water held in reserve; and that, during 320 days of iiaAugation, the
mean height of the prism of Avater raised by evaporation from the surface of the canal
was 812 millimeters, or 31.969 inches.
I understand this to refer to the actual exhaustion from the surface of the canal,
exposed at the same time to Avhatever rain might fall upon it.
25. The quantity held in reserve, of Avhich tAvo-fifths Avere lost by evaporation, is
not stated ; but if it Avere, as I suppose it to be, the full prism of Avater left on the
closing of the navigation, the loss Avould then be one-fifth of that prism in 20 days ;
Avhich would be equivalent to one prism in 100 days, or tlu-ee and one-fifth prisms
during the 320 days of navigation, from this cause alone.
26. But it Avas said that the total abasement of the Avaters in the canal, on a:ccount
of evaporation, Avas 31.609 inches in 320 days. Noaa', taking the rain as given (And.,
p. 237) for Trebes, a central point of the canal, and for a moderately rainy year, as
stated at 697 millimeters, or 27.44 inches, or 24.06 inches for the 320 days, we Imm
the amount of rain which fell upon the surface of the canal, and restored, to that
extent, losses from evaporation. But as, notAvithstanding the rain, these losses Avere
31.969 inches, the tAvo sums may be taken as the total evaporation, or 56.03 inches.
As the time of 320 days includes that of filling, opening, and closing the canal, I pre¬
sume ten months may be taken for its actual navigation. This Avould give a sum of
5.60 inches for the average loss by evaporation per month.
27. We have seen that, for an ordinary summer-day, for the climate of London,
Dr. Ilalley states the evaporation to be tAVO-tenths of an inch, Avhich Avould be 6
inches for a month of 30 days. Noav, taking our climate into consideration, Avhere Ave
have no cooler, and many hotter, days than jin ordinary summer-day in England,
from the middle of April to the 1st of October, and the actual circumstances to AAdiich
Avater in a canal is exposed, Ave believe but feAV engineers Avill consider the evaporation
stated in the deduction just made as beyond the reality for the climate of the Langue¬
doc Canal, and still less so for the one to Avhich our observations may'be applied.
28. But further : In a table of the depth of rain from observations made by j^Ir.
Brantz, of Baltimore, we find the moan annual fall of rain in a series of eight years to
have been 39.89 inches, (Report Board of Engineers, p. 52.) Applying Dr. iralleA''s
2 a
10
rulo of pro])ortion (23) to this, it Avili gÍA'0 a mean ca'aporation of GO.48 inches. Then
applying the rule resulting from the obscrA'ations of Dalton and Iloyle, (23,) the
mean OA-aiioration Avill he 58.038 inches. And noAV, to the same quantity of rain,
a])plying the proportion of Mr. Cotte, (22,) the mean eA^aporation Avill be 88.G4 inches
We have already stated our opinion that eva})oration Avas gi-eater in this country than
in ]']uro])e. All the causes of the phenomenon are knoAvn to he more active AAÚth us,
and Ave have seen that the results from the proportions given betAveen rain and ca'apo-
ration add their proofs to the opinion. Direct-observations liaA-e been made in but feAV
places Avithin my knoAvledge.
29. !Mr. SullÍA-an, in his, report upon the Chesapeake and Ohio Canal, states the
annual evaporation at Salem, IMass., at öG inches; an'd the board of engineers, in their
report upon the Morris Canal in 1823, state that ^Jfr. S. Williams had ascertained the
evaj)oration at Cambridge, ]\rass., to amount annually to 5G inches. Applying this
result to the climate of theiMorris Canal, the board conclude to adopt 51 inches for its
evaporation. " Ihit, as the canal can be navigated only during those eight months of
the year (from April to December) Avhen the evaporation Avill be the greatest and the
rain the least, and as the instruments in use for measuring ca'aporation must aln'ays
give results bdloAv the truth, from their not being exposed to Avind and currents of air,
Ave, therefore, adopt the Avhole sum of 51 inches as expressiA^e of the maximum loss of
Avater by oa'aporation." Xoav, as this Avas for a navigation of eight months' duration,
the loss by oa-aporation Avas assumed at G.37 inches per month.
30. We have seen -that the obserA-ations at ^Montmorency (22) gave an eAmpora-
tion of 41.57, from Avhich, if Ave deduct 2.GG for the tAvo Avinter-months, it aaùII leave
38.91 inches for the remaining ten months. And Ave have also seen that the actual
canal-ca'aporation in that country amounted to 5G.03 inches, (2G,) from Avhich one may
deduce a ratio betAveen the eA'aporation of the laboi'atory and that AAdiich exists on a
canal: this aaIU be found to be as 1 to 1.44. It Avill probably not be considered
unreasonable to take the mean annual evaporation of the climate of Maryland, aa'ithin
the region of the contemplated canal, as equal to that of Cambridge, Mass. Then, if
Ave apply to the Cambridge eAmporation (29) the proportion just ascertained, Ave may
find the probable eA'aporation of the climate of our canal for aa'ater exposed as it is in
a canal. This aauII be 80.G4 inches. Such is the mean annual eA-apoi-ation, aa'hich, if
Ave Avere to calculate for loss from that cause, Ave should use for a canal near Cambridge^
Mass. It could not, therefore, be expected that aa'c should use less for one in the vicinity
of Baltimore. The aA'erage aa'Ould be G.72 inches per month, and G7.20 inches for the"
ten months of navigation.
31. If our reasoning be correct, then, as a general rule, for a climate like that of
Baltimore, evaporation from large and exposed surfaces similar to those of a canal is
to rain as 2.02 to 1.
32. We are fully aAvare that our reasoning upon this matter is speculative. The
data being of that character, the reasoning must partake of the same. Our object is
not to discredit the use of such rules, but to show the caution Avith Avhich they should
be applied.
33. But no rule of this kind can be relied upon ; if true, it is but for sorúe limited
11
locality. Every proportion given by any autliority is thrown into a kind of ridicule by
the facts of some localities. In Cavallo's Philosophy, page 374, it is stated that, from
accurate experiments made by Dr. Dobson during four years, he determined the
annual evaporation from the surface of the water at Liverpool to be 36.78 inches ; and
in page 378, the annual fall of rain at Liverpool is reported to be 37.48 inches. Now,
taking either of these elements for calculation, we can readily perceive into what error
we should fall by the ratio or proportions given .by any author between evaporation
and rain. " The annual quantity of rain," says Di'. Dobson, is a very uncertain test
of the moisture or dryness of any particular season, situation, or climate. There may
be little or no rain, and yet the air may be constantly damp and foggy ; or there may
be heavy rains, with a comparatively dry state of the atmosphere."
34. It is, then, also a very uncertain test of the evaporation, or the evaporation
of the rain. In so important a matter as a canal, the water should not be obtained by
inference.
35. Filtrations.—These are the result of a general law of nature, acting with
greater or less force, according to the peculiarities of soil, but acting unceasingly and
universally; often at great depths, as is observed in mines and caves; in great force, as
is known from the absorption of entire rivers ; through apparently impervious strata,
as has been observed through more than forty feet of the calcareous rock in which are
cut the catacombs of Paris ; and through carefully-constructed masonry, as is to be
seen on passing under our various aqueducts. The idea, therefore, of making a canal
which should be exempt from this general law would be an absurdity. The effort of
the engineer is to lessen its activity and to supply the losses which it occasions.
36. Gauthey, in his work on canals, (p. 267,) gives it as a general rule, that one
may assume for filtration about double the amount of evaporation. This opinion fol¬
lows immediately subsequent to his statement of M. de Cotte's rate of evaporation.
But from the remarks which we have made upon losses from evaporation, and from the
facts we have given, the uncertainty of such a rule must be evident. It appears to
our judgment that it cannot be otherwise than incorrect. There are no acting causes
common to both, so as to produce any iiniform relation between them. Filtrations
are the result of the soil through which the canal passes and the greater or less care
bestowed upon its construction. Noav, it is clear that these have no connection what¬
ever Avith the causes of evaporation, and therefore no rule of proportion can be
assumed as existing betAveen them. The evaporation in the same locality Avould
remain the same Avhether the canal Avere carefully or negligently made, or Avhether the
soil Avere close or permeable. Such a rule can, therefore, be applied to a particular
case only, and to that Avith propriety, merely because it has been found to be true from
actual observation.
37. Most of the rules of French engineers have been derived from obsei'Amtions
made on the Languedoc Canal. Noav, this canal, it is admitted by all Avho have aau-itten
upon it, loses less from the usual causes of Avaste- than any other known canal in the
Avorld, OAving to the care Avliich had been infused in its construction and the vigilance
and intelligence Avith Avhich it is superintended. Rules derived from such a source
should, therefore, be received AAuth great caution. They led the great engineer I have
12
just nainoci into eiTor in Iiis project of the Canal du Centre, and Avould have resulted
in a complete failure if sources of supply of Avater in addition to those at first relied
upon had not been at command.
38. Ihit even in the Languedoc Canal I have not been able to find in my investi¬
gations any data to justify the rule, as the annual loss from filtration given by authors
much exceeds tlie amount which would be derived by calculation from double the
evaporation. Some limited experiments on parts of tlie work would seem to sustain it;
but these appear to me to be wanting in many facts to justify a general rule. There
can be no doubt, however, that all the phenomena connected with canals liave been
observed Avith extreme care on this, the boast of France and the pride of her engineers.
It is esteemed by the latter as one of the most interesting Avorks of that kind. AYe
shall haA'O frequent occasion in our remarks to refer to facts connected Avith its history-
39. It is among canals perhaps the only one Avhich furnishes distinct results of
losses by filtration. The usual method is to combine these Avith those of evaporation
in one common result, Avhich ansAvers all general purposes in forming a judgment of
the supply of AA'ater required. But there can be no doubt if obserA'ations on these and
every cause of loss Avere separated and made distinctly, it Avould lead to much greater
accuracA', and AA'Ould present in a more striking light the great saving of AA-ater which
Avoidd ensue from the introduction of a better system of construction. AATiere canals
liaA'O been made in our country, the supply of AA'ater has generally been abundant, and
the demand for it on other accounts so limited that Ave have been able to afford the
AA'aste of large quantities ; it being a mucli cheaper plan than to sa\'e it at a great
enhancement of cost.
40. Elements to Avhich capital can be applied are not among our deficiencies, but
rather capital in order to bring those elements into actiA'ity. This last is both scarce
and in great demand ; it has, therefore, to be used AA'ith the most vigilant economy.
Hence has arisen AA'ith us a system of engineering AA'hich may be emphatically called
•'the American system," AA'hich looks less to posterity than to our OAvn time, and presses
AA'ith extreme eagerness to an immediate and profitable result. It is a system in har¬
mony Avitli our condition, based upon common sense, and is the only one Avhich, in
our circumstances, can be pursued to any extent in the deA'elopment of our immense
but rather latent resources. AATiile aa'O therefore admire, and learn from, the more per¬
fect structures of Europe, Ave must yet forbear a rigid imitation of them, as there are
but feAv cases in Avhich a different course would not lead to the bankruptcy of all con¬
cerned.
41. The method of engineers. generally, to combine these tAvo causes of los^
of Avater and to introduce but one item into their calculations for both eA'aporation
and filtration, will oblige us to use results of that kind as Avell as distinct statements of
filtration.
42. Hueme, in his History of Canals, (p. 266,) after detailed statements of the
Avater consumed in different portions, while he admits the calculations to be but
approximative, comes to the conclusion that during ten months of navigation the
Languedoc Canal loses by its filtrations alone (deduction being made for losses from
evaporation) about eight times its prism of water, or eight-tenths of its prism per
\
13
month. Now, if we were to reverse the rule of M. Glauthey, and deduce the evapora¬
tion fi'om the filtration, (and, if the rule be correct, it will admit of such an application,)
the loss during the ten months from the two causes combined would be twelve of its
prisms of water, or one and two-tenths prisms per month, which would give an evap¬
oration vastly exceeding that which engineers have used ; and were we, on the con¬
trary, to take the accredited rate of evaporation and from that calculate the filtration,
the result would be much below that which from experience actually takes place.
43. But the different parts of the canal observed show great differences in the
quantity lost by filtration, while there is no reason to believe there could have been
much, if any, difference in the evaporation. The latter quantity, therefore, if used as
a basis for calculation, would have led to great error. The rule, then, of taking twicé
the given evaporation to determine the filtrations is in our judgment extremely unsafe.
We will exemplify it further.
44. The prism of one mile of the Languedoc Canal is about G4,207 cubic yards.
We have seen that it loses by its filtration eight-tenths of tliis per month, or an amount
of 51,365 cubic yards. The surface of one mile is 48,644,893 inches. Now, the period
of suspended navigation being in the winter, when the evaporations are very small,
and may be supposed nothing, we will apply the whole of the mean annual evapora¬
tion of De Cotte to the ten months of navigation. This, being 4L.5 inches, would give
for the ten months an amount of 43,269 cubic yards, or 4,326.9 cubic yards per month
for the evaporation. The filtrations, being double this amount, would give 8,653.8
cubic yards. But we have seen that the amount, by actual observation, is equal to
not less than 51,365 cubic yards. If, therefore, we were to rely on such a rule, it
would lead us into shocking error.
45. Still less can we rely upon the rule of the engineer Ducros, given by Mr.
Sullivan in his report, (Ducros, however, quotes it as the opinion of the engineer Chau-
sade,) of one and a half times the evaporation for the amount of filtrations. That these
celebrated engineers Gauthey and Ducros may not have had facts on which to base their
opinions, we do not pretend to dispute ; but they must have been isolated facts, under
some singular circumstances, and not adapted for a general rule. We can easily con¬
ceive that during periods of extremely dry and hot weather, with water very low in
the canal, filtration would be much smaller than usual and evaporation greater. The
sides and bottom of the canal having been, from long use with a full volume of water,
well compacted, and the interstices closed from the reduced pressure arising from a
small volume of water, but little could pass by filtration, while all the causes of evapo¬
ration were acting with increased intensity.
46. But we have seen that this canal loses during its ten months of navigation
eight of its prisms of water, (42.) We must suppose, also, that it contains a prism
when its navigation is closed. Now, this prism let into the canal during its period of
navigation must be lost also before the subsequent two months have passed; and tliese
being months of little or no evaporation, it must be lost by filtration. The canal, then,
actirally consumes by its filtrations for its ten months of navigation nine of its prisms
of water, or nine-tenths of a prism per month. The prism of this canal for one mile
being 64,207 cubic yards, its loss, therefore, is 57,786.3 cubic yards per month, or
14
1,Í)2G.2 per day, or 80.21 per hour, or about 3G,09 cubic feet per minute, from its
iiltrations for every mile. Tlie evaporations by the rule of !M. de Cotte were found to
bo 4,32G.9 cubic yai'ds per month, (41,) whicli, treated in the .same way, would yield
2.7 cubic feet per mile per minute. The total loss, therefore, on this canal from evap¬
oration and iiltration combined is 38.79 cubic feet per mile per minute; but if we take
the evaporation of i^l. Pinn of one-fifth of ,a prism in 20 day.s, (25,) the total loss from
the two causes combined will be about 48 cubic feet per mile per minute.
47. AVo have gone into these details, because it Avas satisfactory to know Avhat
that canal, Avhich, as is generally admitted, loses the least of any knoAvn canal, actually
lost from the causes stated. But its loss being a minimum, rules derived from it would
certainly bo very unsafe guides to follow in judging of other cases, however valuable
they may be in indicating the advantages to be obtained from a careful construction.
48. The board of United States engineers, in their report upon the Che.sapeake
and Ohio Canal, (see Pep., pp. 39, 40,) assume, as data for their estimate, the con¬
sumption of once its water-prism per month, on account of losses from evaporation
and iiltration.
49. From experiments made on the Erie Canal, and communicated to me by
that distinguished engineer, Afr. J. B. Jervis, (to Avhom I am also indebted for other
highly valuable communications,) it would ap})ear that the least loss, from observations
made at various places, was 100 cubic feet. This Avas not the measurement of loss
from a distinct cause, but from all united—leakage of locks, CA'aporation, and filtration.
The dimensions of this canal are, 40 feet Avater-surfiAce, 28 at bottom, and 4 feet deep;
AA'hich give, for its prism of one mile, 2G,595.5 cubic yards. The loss of 100 cubic
feet per mile per minute is equal to 1 GO,000 cubic yards per mile per month; or, .sup¬
posing the navigation to continue for nine months, (in that climate,) the total loss Avould
equal about 54 times its AA'ater-prism per j'ear ; adding to this the loss of the prism in
the canal at the closing of the navigation, gÍA-es a total loss of 55 of its pibsms of
AA'ater for all causes, except the demands of the locks for its trade.
50. This consumption of Avater is certainly very great. The commissioners, in
their annual report of January, 1834, make the folloAving remark:
" The commissioners are inclined to the ojiinion that, Avith proper care in guard¬
ing against the Avaste of AA'ater, 100 cubic feet per mile per minute for leakage, filtra¬
tion, and OA'aporation (all causes of consumjAtion) Avould be a safe estimate for the
Avestern and middle sections of the Erie Canal ; but it is believed it Avould be found,
on a careful examination, that a much greater quantity Avould be necessary on man}'
parts of the eastern section, Avhere the soil is more open, the leA'els shorter, and the
locks more frequent."
51. ShalloAv canals lose more than deep ones. This is a point noAv so well settled
by experience that facts need not be adduced to proA-e it. AA'^e mean, more in j)ropor-
tion to their dimensions ; that is, in proportion to their filtrating surfaces. In our OAvn
country Ave have an example of a deep canal, (the Chesapeake and Ohio Canal,) the
depth of which is six feet.
52. Mr. Fisk, the chief engineer of that canal, after repeated and careful observa¬
tions over an extent of about forty miles, represents its loss, on account of its eA'apora-
15
tion and filtration, at 60 cubic feet per mile per minute. Its dimensions are 60 feet
at the water-surface, 32 feet at bottom, and 6 feet deep, wbicb give, for one mile, a
water-prism of 53,973 cubic yards. And as this canal loses 60 cubic feet per mile per
minute from evaporation and filtration, it will amount to 96,000 cubic yards per month
per mile, which is more than one and three-quarters of a prism.
53. Now, if Ave suppose the navigation of this canal to continue during ten
months, and add to the loss just stated that of the prism of water left in the canal, it
will make 1prisms of water for its navigable year-.
The observations of Mr. Fisk Avere made upon that part of the canal, betAveen
Harper's Ferry and Seneca, Avhich has been the longest in use. Much of it also passes
through loAv gi'ound, and may, therefore, be considered as the drain of the adjacent
high grounds ; and where exposed to the causes of active filti-ation, it Avas puddled
Avith great care. On these accounts, I conceNe its loss may be fairly considered,
under our system of construction, as a minimum ; and that the safer rule for a geaieral
estimate, on account of losses from filtration and evaporation, would be 2 prisms per
month. Its actual loss being, then, 1.85 prisms, our safer rule adds 0.15 of the prism
of one mile per month, Avhich AAmuld increase the stated loss per mile per minute 2.25
cubic feet ; or make the Avhole, exclusive of the prism left in the canal on the closing
of the navigation, 62.25 cubic feet per mile per minute. This prism, left in the canal
at the closing of navigation, is, as has been shoAvn, equal to 53,973 cubic yards (52)
for one mile. As its loss is for the Avhole ten months, it Avould be 3.374 cubic feet per
mile per minute, making the total loss per mile per minute equal to 65.624 cubic feet.
54. LeaJcage at locks.—It is highly important that losses from this cause should be
considered in every estimate of Avater for a canal. Unlike filtrations, these are least
at first, and increase as the cabal is ixsed. The AA^ater passes under the miter-sills,
betAveen the gate-posts and the holloAV coins, betAveen the gates AA'here'they meet, from
the valves, and under the bottom of the gates. All these are closer when neAV, and.
from gradual Avear and other causes, open more and more every day, until repairs, and,
ultimately, new gates become necessary. It is also Avorthy of remark that, iii a series
of locks, all depending uiDon the same source for supplies of Avater, it is the lock of
greatest leakage Avhich must bo considered. If the second lock of a series, for instance,
leaks more than the first, then the leakage from the first Avill not keep up the interme¬
diate level, as more than it supplies is draAAm off by the second lock. So, also, if the
lock of the greatest leakage be the third or fourth. And Avhen many locks are depend¬
ent upon the same source, it Avould be absurd to suppose that' each Avas constructed,
and its gates fitted, Avith the same care. So that a slight accident to any one of a series,
not sufficient to justify the stopping of the navigation for repairs, increases the leak¬
age, Avhich the summit has to supply. On these accounts, there can be no average of
the leakage from many locks as the basis of an estimate, or as proof of Avhat a canal
loses from this cause. It must lose that whicli leaks from the lock of greatest leakage,
and cannot lose less.
Losses from this cause, in long levels, are not so serious nor so sensible to obsei*-
vation as in short ones. In these last, they are both soon observed and felt.
55. Andreossi (p. 223) reports the result of observations on this account, of loss
IG
oxperioncGtl ou the Languedoc Canal, Ly tlio engineer, Sir. Pinn. These observations
were made upon many locks, and the mean of the whole is stated to bo 10 liters, or
610.28 cubic inches, per second. The objection to thi.s result is that it is a mean of
the whole, instead of being the loss from the lock of greatest leakage, Avhich, as wo
have already shoAvn, is the actual loss sustained.
,5G. Ten litere per second is equal to 30,514: cubic feet per day ; or, for the two
locks, one at each end of the summit. Gl,028 cubic feet, (our measui-e,) which, in a
month of tliii-t}--days, would amount to 1 ¡830,840 cubic feet, or to 67,808.88 cubic
yards, (say 67,809,) which, for the ton months of navigation, would bo 678,090 cubic
yards.
.57. The size of the locks of the Languedoc Canal is very great, and their cmwed
sides give an unusual cubic content. Owing to this form of construction, (bad in
itself, and long since .abandoned,) we c.annot well make a comparison of its prisms of
lift with the leakage of its locks,
.58. There is another reflection jiroper to bo m.ade. All other things being equal,
the le.akage must be in jn-oportion to the perpendicular height of the water, or to the
pressure to which the orifices or openings are oxpo.sed; and also the leáking-surface
(that is, the joints) must bo in proportion to the lift of the lock and the width of the
gates.
59. These circumstances render the applications of observations on canals of
extremely doubtful propriety, where we are not fully possessed of a knowledge of all
influencing dimensions and causes. Upon the same canal, the width of the lock-gates
must be the same, but the lift of the locks need not be, and often does vary eonsid-
eriibly. Now, in the very canal we have named, the second lock from the summit in
one direction has a lift of more than 9 feet, while that of the first is about 7.J feet;
the ninth lock also has a lift of between 11 and 12 feet. It is clear, therefore, that the
aver.age from the le.akage of such variable lifts must give a ftlse result (and false to a
great amount) of the absolute quantity reiilly drawn from the siunmit to supply the
leakage of the locks, which, as we have before remarked, can never be less than that
of the lock of greatest leakage-. At the opposite end of the summit, among the locks
depending upon the summit for its water, there is one of more than 12 feet lift. The
summit is, therefore, really subjected to the leakage from tliese two locks of so great a
lift. We will take the two exti-emes of 7 J and 12 feet to illustrate our reasoning by
an example."
CO. The discharge' under the two pressures 7^ and 12 feet, being to each other as
the square roots" of the pressures, are about as 27 is to 35, or the discharge from the
latter is about one-tliird more than ft-om the foimer ; which "ivould make a loss of
904,120 cubic yards for the .ten months by taking the lock of the greatest leakage.
61. Although we cannot make a just comparison of this loss with the prism of lift
of the locks of this canal, on account of the reasons heretofore stated, we will see, how¬
ever, what it would be if the sides of the lock-chamber were a right line, and the
chamber an oblong square instead of an oval.
62. Taking the dimensions of the first lock from the summit and reducing its
cube by straightening its sides, we shall find its lookful, or prism of lift, to be about
17
346 cubic yards. The corrected prism of lift being, then, 340 cubic yards, (Gauthey,
p. 48,) and the leakage at the lock-gates being 1,130 cubic yards per day, it amounts
to nearly 3^ lockfuls (prisms of lift) per day for one lock. But the iiicrease of this
leakage on account of the lock of greatest leakage will bring the amount to 1,507
cubic yards per day, of rather more than 4^ prisms of lift, or 8| for the two locks, one
at each end of the summit. If our Gews of the case be, therefore, correct, this uncom¬
monly well-made and carefully-attended canal loses this last quantity daily from its
summit by the leakage of its locks.
63. Messrs. Fisk and Hughes, in their report of March, 1837, (pp. 16, 17,) fix the
leakage at each set of locks adjacent to the summit at t^velve lockfuls (prisms of lift)
per da}". This was the result of very careful observations upon the locks of the Ches¬
apeake and Ohio Canal made by Mr. Fisk, its chief engineer. All the locks of this
canal are about the same lift and the same dimensions in other respects ; i. e., 15 feet
wide, Avith a lift of 8 feet. Noav, as the Avorkmanship of these locks is probably the
best in our country, and as that of other canals ought to be as good, Ave ma}": take
them as eA'idence of the degree of perfection to Avhich Ave are Avilling to go in such
matters, or Avhich aa^o are able to afford. As Ave believe, also, that the gates are as
carefully attended to on this canal as on any other in our country, its results are on
that account likewise a good criteidon. The observations, lioavoa'er, aa'cre made during
a period of suspended navigation, Avhen the gates Avere closed Avith great care and kept
so for several Aveeks aa'hile repairs Avere being made. Mr. Fisk has assured me that,* in
his opinion, the actual leakage of the gates Avhen in acti\dty exceeds the amount stated,
great as it may be considered ; avc have, therefore, the assurance of the cliief engineer
of the canal that it is less than that Avhich really occurs to the canal Avhen in use.
64, We have ourseh'es frequently observed the leakage at the locks of this canal,
and Ave are satisfied that Jlr. Fisk has not exaggerated the loss. Twelve lockfuls
per day for each lock is half a lockful (prism of lift) per hour. Noaa", to bjing this
rate of leakage more Avithin the judgment of the general reader, and to enable him to
test it by Avhat he may himself have observed on canals, Ave Avill make a comparison
in a shape in Avhich the quantity aaûII be more readily comprehended .than that of the
rate of cubic feet per minute. Half a lockful per hour is 62Í cubic feet per minute ;
the lock-chamber, being 100 feet long by 15 Avidc, Avill give a su[)erficies of 1,500 feet.
NoAV, "this rate of leakage Avould not raise the Avatcr in a lock of this size more than
one foot in tAventy-four minutes, or half an inch per minute.
65, This leakage is tAvice and a half as great as that of the locks on the Langue¬
doc Canal. Wo acknoAvledge it to be great; bqt, as the Avorkmanship of the locks on
the Chesapeake and Ohio Canal is as good and the vigilance of those Avho attend iqiou
them as active as Ave have a right to expect for the canal in contenq)lation, Ave can see
no other correct course than to adopt, in our reasoning iq)on tho Awater for that canal,
the leakage just given.
66. "^Gie locks in the two cases, tho Languedoc and tho Chesapeake and Ohio
Canals, are sufficiently similar in their dimensions to attribute anuch of tho difierence of
leakage to differences in tho manner of building. One is thoAvorkof a government, tho
other of an incorjjorated company; one Avas built by tho agents of a government, tho other
by contractors; Avith one, no expense in materials or skill in execution Avas spared; in the
3A,
18
otlior, too yonenilly tlio lowost bidder was taken, wlio must, of" course, soeuro his own
profit in the kind of work and (piality of materials. In works of this character, no sys¬
tem is so pernicious, or in the end so costly, as that of gdving' 'work to the lowest bid¬
der, under the dehisi\'o expc(;tation of saviu;,^ Good work cannot be done for less
than a just valuation ; and when bids for le.ss arc made, they can result only in the
ruin of the contractor if ho 1)0 faithful, or to the prejudice of the work if he be not.
The former is avoided with extreme care; the latter more generally occur.s, and it.s
consoiiuences are enormous expenditures under the head of "re2)airs," to which our
[)ublic works are so frcMiuently subjected, always exceeding the su])2)osed savings on
the accepted bid.s. An intelligent and skillful contractor will not offer to do work for
less than its })ro2)er value; the uninformed, the inexperienced, or the unfaithful may;
and, fnnn the s^'stem ijursucd, in the hands of these latter our public works are gen¬
erally thrown. No boa.st is so reidete with false reasoning, so delusive to society, as
that frecpiently made of having let work at prices much reduced from those of the
engineer's estimate.
If the engineer be competent, his estimate is no more than a fair cost of the work ;
then, if that Avork be let for less, it can only bo to the prejudice of the Avork.
()7. Our Avorks must, also, partake of the degree of skill and ex^jerience in our
mechanics, Avhich is Avell known to be rather beloAv the standard recpured for similar
structures in Kurojie.
(J8. On these accounts, therefore, as aa cU as the necessity of economy in first cost,
it may easily be conceded .that our canal-structures are not earned to that degree of
perfection Avhich is found in other countries, lly the Avay, ipion this matter of economy
in first cost, it may be Avell to say a a\-ord or tAvo. It should not be understood as
meaning numbers of dollars in comparing mile with mile or lock Avith lock, but in the
(piantum of labor Avhich the same amount of money aauII command in the Iavo countries.
In our country, the Avages of mechanics and of laborers are so much higher than in
Nurope that the .same amount of serA'ice cannot be obtained for the same cost; and,
of consequence, Ayorks of the same cost in money must be inferior, because of the less
labor upon them. Unless this idea is maintained, aa'O ahvays deceiA'e ourseh'es in
making comparison Avith similar Avorks in Europe. While, therefore, I readily admit
that the Avork of the ChesajAeake and Ohio Canal is ¡Arobably the best of that Idnd in
our country, yet it may, hoAvever, be said that it is inferior to similar Avorks in Europe.
G9. AVe may, then, Avithout violation of ¡Arobability, ¡Alace this difference in the
leakage of the locks to differences in the r^uality of the structures ; and Ave may, also,
from the character of the work on the Chesapeake and Ohio Canal, assume its lock-
gate leakage as a fail' basis for estimates in our country.
7Ü. But to return to the subject. TAvelve lockfuls (prisms of lift) for the lock at
each extremity of the summit is 24 lockfuls jAcr day. Each lock being 100 feet long,
15 feet Avide, Avith a lift of 5 feet, Avill give 7,500 cubic feet for its jArism of lift, or
lockful of Avater. This Avill equal 180,000 cubic feet jAer day, or 6,GGG.6 cubic yards ■
Avhich, for a month of thirty days, Avill be 199,999.8—say 200,000 cubic yards.
71. Accident may increase the leakage of a lock so much as to make the jArocess
of filling it tedious ; and yet the injury may not be sufficiently great to justify the stop-
jAing of the navigation in order to make rejAairs.
19
72. The leakage arising from tlie defective shutting of a valve would increase the
loss considerably beyond the amount we have assumed ; yet it would not, in our judg¬
ment, be fair to embrace such a case in a general estimate of leakage, while we are
willing, Jiowever, to admit its probability in the course of a season with some one of
the many locks that may be dependent upon the same source for their supply of water;
But, at the same time, the probability of such accidents shoiild not be disregarded by
the engineer ; and while he cannot fairly include them in his estimate of the quantity
of water actually required, it becomes his duty to show a surplus in order to meet
them, or to point out the deficiency and its consequences.
73. Lodes.—Much has been Avritten upon locks, the manner in Avhich they should
be arranged, and their lift, in reference to convenience and to the AAmter they consume.
The general result of the Avhole is that the most fiworable lift is from 7 to 8 feet ;
that they should be as far from each other as the nature of the ground Avill admit, and
so far as not to impede the navigation by the abstraction, from an intermediate level,
of a lockful of water; avoiding, if possible, aggregate locks, or locks immediately
adjacent to each other ; and, that among a series of locks dependent upon the saine
source for supplies of Avater, the lift should never increase as they descend. It may
decrease adAmntageously, but this is a nicety belonging to the engineer in arranging
his plan. The illustration of all these positions AA'ould lead to remarks purely profes¬
sional, inapplicable to the object of the report, and therefore unintei'esting. We shall,
on these accounts, avoid it, leaA'ing Avhat may be necessary, if any shouhT be, to the
particular case Avhich the plan may develop.
74. The simple question upon AA'hich it may be proper to say something at present,
is, on the supposition of Avell-arranged locks at proper distances from each other, Avhat
quantity of Avater Avill the passage of a boat require ? . .
75. Engineers have given various opinions on this subject—one prism of lift, one
and a half, one and three-quarters, tavo—all depending upon the degree of presumed
regularity in trade. The matter is familiar to them. We hope they Avill not suppose
it our object to instruct them on a subject upon Avhich they are knoAvn to be so Avell
informed. We desire only to make it equally plain to others.
■ 70. To aid in the illustration, Ave Avill make use of the folloAving diagram :
iSummit level.
An alternate passage means one Avherein the tAvo boats pass each other on the
summit-level, or pass the locks alternately.
First. When a boat in the level K arrives at the lock A, the lock has to be filled
in order to raise the boat to the summit. The same process has to be gone through
Avhen a boat in the level Y arrives at the lock B, in order to raise this second boat to
the summit also. These two boats on arriving alternately at the locks A and B, find
them already filled by the ])rocoss Ave have just described, and immediately ])ass into
them. Then, on descending to the adjacent levels, K and Y, each boat e.xhausts the
lockful (prism of lift) Avhich had been used to raise the other. This is the case of
20
t\vo lookful.s for uii nltcrnnto passage, or one lockfiil for eacli boat., and is tlio least
(juantity wliicli can l)e exliausted per boat under tlie most favorable circumstances.
77. One boat making tbe ])assago would consume no more. On arriving at a lock,
tbe lock would be tilled in order to raise the boat, and would remain tilled after the
boat bad ¡lassed out into tbe upi)er level, 'fben, on descending at the opposite end, it
Avould e.Kliaust a })rism of lift or lockfnl.
78. We liavc said tlnit one prism of lift, per boat is tbe least wbieli can be exhausted
under the most favorable circumstances ; for, if the lock A or 11 were full on a boat.
2)rc.senting itself to be raised, tbe case becomes altered ; then the lock inu.st be emjitied
to admit the boat, before it can be raised; and after this, by Avhich one lockfnl is
drawn oil", another lockfnl must he drawn off to lower the boat at the ojí^msite end of
the summit. We .se(!, therefore, that the ca.se of one lockfnl 2>er boat is on the su])-
po.sition of a regularity in the 2)as.sages and attention to the locks that is hardly po.ssible
in practice; in fact, it may be considered as never occumng. •
79. Second. Wo will now supjxysc the case of two boats jiassing in succession
FoV the first, the lock has to be tilled ; it tlieu passes to the summit. Ihit for the sec¬
ond, this lockfid lias to be let. off that the boat, may enter the lock, which has then to
bo filled again in oi'der to raise the boat, d'lie t^vo boats, therefore, are raised to the
summit by the exhausting of one lockfnl of water. On arriving at the other end, one
lockfnl for each boat is e.xhausted, to enable the two boats to descend ; in all, tbree
lockfuls, or ^wisms of lift, for the passage of two boats in succession. This is a case
of one lockfnl and a half for each boat, and which also requires the mo.st favorable
circumstances; for, as in the first, case, if the lock were filled when the first boat ¡ire-
sented itself to be raised, it would have to be let oil" before the boat could enter, which
adds another lockfnl to the quantity exhausted by the successive ¡passage of the two
boats, or tAvo lockfuls for each.
Third. Suppose three boats to [»resent, tliemselves at the same lock in succession.
The first is to be raised by filling the lock ; the second, by e.xhausting that used to
raise the first, and filling again ; the third, liy exhausting that used to raise the second,
and filling again. The throe boats are therefore raised by exhausting from the summit
two lockfuls. Ihit, on arriving at the ojqiosite end, one lockfnl is necessary to let each
boat down. The passage of three boats in succession Avill then require five lockfuls,
or six if the lock be full on the ajjproach of the first boat.
Fourth. If Ave suppose a 2)assage of four boats in succession, soA'en lockfuls, or
one and three-quarters to each boat, Avill be required ; or tAvo for each if the lock be
full on the a^Aproach of the first boat.
80.. We liaA'e seen, therefore, that as small a quantity as one lockfnl for the [lassage
of a boat is scarcely a [Aossible case ; that a lock and a half for each boat is the least
that can be used in the successive [Aassing of tAVO boats ; that a lock and three-qiAarters
is the least that can be used in the .successive ¡Aassing of four boats ; and that, in every
case, if thé lock be full on the approach of a boat, tAVo lockfuls Avill be required for
the [Aassing of the summit by OA^ery boat. .
81. To generalize the case for any number of successive [Aassages, it is that the
least quantity of Avater which can be used is tAvice as many lockfuls less one as the
21
number of boats (or two lockfuls for eacb boat) when the first boat finds the Ipck
full on its approach.
82. Our trade is not only periodical but is at all times in fleets, from the nature of
business and the social habits of boatmen. Who ever observed on our canals an alter¬
nate direction of every boat ? They are generally, I may say universally, in groups
or fleets ; three, four, or five in one direction, then tliree, four, or five in another. Pas¬
sages may balance each other on the same day in different directions, but this does not
constitute alternate passages. If five boats pass in one direction in one hour and five
in the opposite direction in the next hour, it does not constitute the alternate passages
upon which the estimate of one lockful of water for each boat is founded. These are
successive passages for the whole number of boats except one. An alternate passage
is when two boats pass in opposite directions before either is succeeded by another
boat; or Avhen any number of boats pass alternately Avitliout any o»e to folloAV another
until after a boat from the opposite direction has passed. When fleets from opposite
directions meet at a lock, alternate passages are adojited by the rules of most canal-
companies ; but Avlien they meet on a level, they pass each other in fleet and the locks
at each end in fleet. On meeting at a lock, equality of rights demands alternate pas¬
sages ; but on meeting on any level of the canal, equality of rights demands no such
sacrifice of time, nor is it necessary, nor would the trade submit to it, nor has any
attempt to exact it ev^er been'made.
83. But the passage of fleets in different directions, or of a fleet and a boat, has
its influence upon the quantity of water required. We Avill see what it is, (our reason¬
ing is applied to the ¡massage of a summit;) but we Avill first; hoAvever, again explain
Avhy it is that one altern¿ite passage, Avhich is the passage of tAA'o boats in different
directions, consumes less Avater than a consecutive passage, or the passage of tAvo boats
in the same direction.
84. In the first case, each boat is raised to tlie summit by merely filling the lock.
The Avater has not yet been exhausted or draAvn off, or let doAvn beloAV the summit; it
has only been let into the lock. On passing to the opposite ends of the summit, the
locks are found as they Avere left, filled Avith Avatcr ; each boat, on descending, takes
only the lockful Avhich it found ready doAvn Avith it. As these tAvo boats, therefore,
Avere raised Avithout draAving off any Avater from the summit, and Avere let doAAur Avith
one lockful each, tlie tAVO consumed but two lockfuls . in the passage. Tliis is the
alternate passafje oí i\io orighxQQY.
85. In any other order.of passing, as has been before explained, and Avhich must
be successive, the two boats cannot consume less than three lockfuls, or one and a
half each. Noav, as it can only be tavo single boats meeting each other Avhich can
make an alternate passage, it can, tlierefore, only be the two first boats of two fleets ;
the remaining boats of the fleet make consecutive passages. Tlie case, therefore, of
tAVO fleets meeting on a level or passing in opposite directions resolves itself into tliat
of a fleet meeting one boat, or into one alternate passage and consecutiA'e passages
for the balance of the fleet. It matters not Avhether this alternate passage bo Avith tlio
first or any other boat of the fleet; the effect is the same.
8G. First. The smallest licet is that of tAVO boats. If a fleet of tAvo boats moots
one boat, it constitutes one alternate passage and the consecutive passage of one boat-
22
Tho quautit}' of Avator consumed is, tlierofore, tlireo lockfuls for tlio three boats, or
onu lockful per boat.
Second. If a fleet of three boats meets one, it is one alternate pMago and a con¬
secutivo passing of tAvo, The four boats, therefore, constimo five lockfuls of Avater, or
one lockful and a (piarter each.
Third. If a fleet of four boats meets one, it constitutes one alteniate and three
consecutivo passages ; or tho ih'O boats Avill consume .seven lockfuls of Avater, Avhich is
one lockful and tAvo-lifths each.
Fourth. If a fleet of fu-e boats meets one, it con.stitute.s one alternate and four con-
secutive passages ; or nine lockfuls for the six boats, being one lockful and a half each.
Fifth. If a fleet of six boats meets one, it constitutes one alternate and five con¬
secutive pas.sages, and aaûII consume for the soa'Cu Imats clca'cn lockfuls of aa^ater, or
ono lockful and four-sovcntlis to each hoat.
Sixth. If a fleet of seven boats meets ono, it constitutes one alternate and six con¬
secutive passages; or tho eight boats Avill consume thirteen lockfuls of Avater, or one
lockful and fiA*e-eighths for each boat.
SoA-euth. If a fleet of eight boats jneets one, or if (Avhich gÎA'ea tho same result)
eight boats pass in ono direction Avhilo ono passes in tho opposite direction, the nine
boats Avill require fifteen lockfuls of water, or one and six-ninths or one lockful and
tA\*o-thirds each".
Eightli. And a licet of nine boats meeting ono, or nine passing in one direction
and one in another, tho ten boats ivill require seventeen lockfuls, or one lockful and
soA-en-tentlis for cadi.
87. We see by tho foregoing, therefore, that more thai^ one lockful must ahvays
bo used ; that tho second supposition requires one lockful and one-quarter for each
hoat; the fourth, ono and one-half; and the eighth nearly one lockful and three-quarters.
88. XoAA*, this is all the rigid result of theory on tho supposition of the most fiia-or-
ahlo circumstances, Avhich can never bo obtained in practice. Irregularities Avill crecqi
in—they are unaA'oidahlo ; and, as previously explained, these irregularities soon tliroAV
every case into that of a maximum exhaustion, or two lockfuls of water for each boat.
We are not theorizing, but endeaA'oring to exhibit practical effects ; AA*e must pay atten
tión, therefore, to such practical resxdts as are highly probable.
89. There is another and not inconsiderable'cause of aa-aste, AvMch is Avitli most
propriety to be placed to tíie accmmt of lockage, as it is occasioned 'by tlie passing of
boats ; Ave mean that of tho column forced oA'er waste-Aveira, over lock-gates, and down
the feeding-fliunes, by tho Avavo from the motion of the' boat In an active trade, this Avill
he foiuid to bo a very serious cause of waste; to Avhicli may be added that arising
from the fact of tlio lower gates, after a boat has entered, ahvays being somowliat open
until forced to by the current created by letting water in at the upper gates, by which
miich aa'ater is lost.
90.- It is somcAvIiat singular that, while tivo lockfuls per boat is the maximum of
theoretical reasoning on this suhjecl^ it is yet, hoAVCA'er, the result of common irregu¬
larities of trade and of slight inattention on the part of lock-keepers. Does any one
doubt that these irregulai-ities and inattentions are of common occurrence ? If so, let
Mm pass a few weeks on any of our canals, and his doubts Avill ba removed. The
23
maximum of theory, then, being no uncommon result in practice, Avould it be proper—
would it be safe—for an engineer to estimate a less rate for Iiis lockage 1 We think not;
and we, therefore, adopt it as the rate by which our judgment of water exhausted from
this, cause will be governed. - ,
91. A distinguished writer on this subject has introduced, in his calculations of the
water consumed in the passing of locks, a deduction of the quantity displaced by the
submersion of the boat. Although we cannot dispute the correctness of the consid¬
eration, yet, when a view so rigorous has to be taken in order to prove the sufficiency
of water for a canal, it becomes, in our judgment, a worse than doubtful project.
92. There is also a serious loss of water arising from a cause hardly attributable
to either of the heads named, and particularly to be noticed in Avide canals ; Ave mean
that occasioned by high winds, Avhich dash the waves over the toAving-paths, doAvn the
feeding-flumes, and over the lock-gates.
93. Under all these considerations, therefore, Ave" repeat the opinion that Ave adopt
tAVO lockfuls of Avater for the passage of the summit by each boat ; and Ave cannot,
without a reproach from our OAvn judgment, adopt less.
94. Feeders.—It is a Avell-knoAvn fact, attested by universal experience, that the
loss of AA'ater from feeders is greatly disproportionate to that from canals: Ave mean
simple feeders, Avhich are small canals to pass Avater, and too small for the usual canal-
craft. Various causes are assigned for this peculiarity: the greater velocity, by Avhich
the.AA'ater being more agitated, occasions increased evaporation; the smallness of the
column, AAliich, becoming sooner and more heated by the sun, produces, on this account,
also a greater amount of evaporation; the less consolidation of the bottom and sides,
from the diminished volume of Avater causing less pressure, from Avhich filtrations are
the greater ; the purer and clearer condition of the Avater, carrying little or no sediment
or dissolved earth, by Avliich, in canals, the filtrating-pores of the exposed surface
become gradually closed. These, and others more philosophical and abstract, are given
as accounting causes. . Be they, hoAvever, correct or not, the fact is as stated, and it
should .be taken into consideration in reasoning upon feeders.
95. The best-constructed and oldest feeders knoAvn are those of the Briare and
Languedoc Canals of France. Of these, it has been remarked that, Avith the exception
of covering, no other precautions to prevent losses of Avater can Avell be iniagined.
96. The noted feeder of the Briare Canal is called "the feeder of St. Prive."
Its length is about eleven miles, and its average dimensions about 12 feet at Avater-sur.
face, 9 feet at bottom, and 3 feet deeji. After frequently-repeated and most exact
gauging, it Avas found to lose three-fourths of the Avater itreceiAmd ; oi-, in other Avords,
it delivered into the canal but one-fourth of the Avater Avhich it received from its source
of supply. This loss is equivalent to about 0.68 per mile of the quantity receiAmd.
97. To the Languedoc Canal there are tAvo feeders, the Plaine and the Mountain
feeder. The entire development of these is 88,225 yards, rather more than fifty miles.
Of this development, 32,876 yards are artificially constructed; the balance being the
old beds of streams, in Avhich, Avhatever may be the filtration, it has long since arrived
at its minimum. Of the 32,876 yards, 20,254 yards are made through a compara¬
tively impermeable granite; that is, about one-fourth of the Avhole length. Various
concurring circumstances are stated by Iluerne and others as Avell adajited to reduce
24
flio nitnitions oi tlioso feeders. Nov is tlio loss tlioy e.xpen'eiico alluded to as oxtraor-
diuaiy; yet, from a eritieal comparison of tlio water received and delivered, tlio actual
loss per year is moro tliau 100 tiincs tlio water-jirism, (llueriio, p. 270,) or moro tlian
10 ¡irisms per mouth for a navigation of ten months. Now, this loss must he chiefly
on that part which is not made through the comiiaratively impermeahle granite, and
may, therefore, ho charged upon i!8,000 yards, ahout throe-fourths of the whole dis¬
tance, Avhieh -ivould make ahout 125 of its water-[)risms during the navigahle year, or
12.] jirisms per month.
08. The size of a feeder may he assumed at 12 feet witter-surface, 8 feet at hot-
torn, and 5 feet deep. This would give a cuhe or prism per mile of 158,400 cuhic
feet, or 5,80G.(J cuhic yards. Now, 12.] times this iirism would he 7."),3;>2.5 cuhic
yards j)or month, or 45.8 cuhic feet per minute.
91). itcsnvolrs.—Wii shall view these under the limited asjiect rerpiired hy our
ohject: their ability to retain water, and the (piantity Avhich it is prohahle they Avill
receive in iirojiortion to the rain upon a given surface. Ujion this last iieculiarity,
climate has, Avithout douht, a great intluence. In northern climates, the ground is
longer and harder frozen ; the accumulation of snoAV upon its surface proportionally
greater, Avhich passes into the reservoir from gradually melting Ijy the Avarmth of
spring, losing less hy filtration, as less Avill pa.ss through the frozen surface of the soil.
On those accounts, there can ho no douht that more aa-ater Avill he collected in reser¬
voirs in more northern climates; for, in more southern, a greater portion of that Avhich
falls on the surface of the soil Avill pass oil" hy iiltrations. These considerations aa'ouUI
make more lakes in a nortliern climate, more and larger springs in a southern ; Avhich
inference Ave heliove to he actually sustained hy the general physical pecidiarities of
the glohe.
100. The point first to he estahlished is, Avhat proportion of doAvnfall-Avater upon
a given surface can he collected in a reserA'oir ? Upon this Ave have searched in vain
among the Avorks of European engineers for the result of direct observation. All is
estimate, conjecture, .^peculation ; the general result of Avhich, hoAvever, is that ahout
oue-third of the Avater Avhich falls may he collected in a suitable reservoir. The form
of the surface of the soil has not so much influence as many Avould suppose, except in
the rapidity of the drainage. Numerous streams are found in a rolling countiy, exten-
sía'O saa'amps in a flat; and the greater evaporation Avhich Avater in the latter experiences
from longer exposure ahout compensates for the less filtration of the former from a
more lupid floAving-off. Of course, Ave have not in mind extreme cases of either.
101. Sutcliff, (p. 84,) speaking of the Rochdale Canal, after a calculation ou the
subject, says, "aaIiícIi plainly prOA'es that, notAvithstanding' the close texture of the
soil, little more than one-third of the rain aa-hich fiills upon them (the commons) can
be got into the summit-level ; and, Avere these commons cultÍA-ated, I do not think that
more than one-sixth part of the rain that Avoidd fall upon them could be drained oft"."
102. When the Chenango Canal, in the State of Noav York, aa'as about, being
made, and Avhich Avas to depend principally upon aa'ater collected in reser\'oirs for its
supply, the engineer, ]\rr. J. B. Jervis, estimated one-fifth of the doAvnfall-Avater as the
quantity AAdiich could he collected ; hut, with a aúcav of ascertaining the matter more
accm-ately, he had experiments made in the a'^alleys of tAvo streams, Madison Brook and
Eaton Erook, wbick "will be found in the report of the New York canal-commissioners
of January, 1836.
103. Arrangements for gauging were established in each brook; and the results of
the daily gauging at each place, and also that of the rain which fell at the same time,
will be found in the follo"\rdng' tables :
Table E"o. 1 Eaton BrooTc Valley.
1S35.
ó
M
n
fco
'S
pH
Falling water
on an area of
6,800 acres.
Amount of same
passing sluice
from same area.
Percentage of
drainage to
fall.
Months.
Inches.
6.72
2.74
2.86 .
1.34
3
2.20
.96
Cuhtc feet.
165,876,480
67,634,160
70,596,240
33,076,560
74,052,000
54,304,800
23,690,640
Cubic feet.
59, 407,394
27,994,240
13,547,053
9,586,513
20,694,051
23,772,620
30,525,544
.358
.414
.192
.29
.272
.438
1.541
August
September
October
November
•December
June to December, inclusive
Juno to October, inclusive
489,236,880
191,528,020
.392
411,235,440
131,229,856
.319
* Drained the snow of November.
Table No. 2.—Madison Broolc Valley.
1835.
O
to
S
cj
to
Falling water
on an area of
6,000 acres.
Amount of same
passing sluice
from same area.
Percentage of
drainage to
fall.
Months.
* Snow on ground, ■whicli fell in November
Inches.
Cubic feet.
87,120,000
47,262,600
54,450,000
22,443,400
108,900,000
43,124,400
175,329,000
84,288,600
60,040,800
19,100,400
84,070,800
■ 45,738,000
16,552,800
Cubic feet.
January
February
t March
2.17
2.50
1.03
5
l.üs
S. 05
3.87
3.06
.83
3.86
2.10
.76
23,192,079
35,377,594
43,234,650
80,770,974
58,013,176
20,138,006
23,141,302
23,725,060
19,158,957
' 19,541,880
18,232,372
19,401,304
.491
.649
1.928
.741
' 1.345
.115
.274
.356
.999
.232
.399
1.172
+ May
t August
t September
{ October
t Novenibcr
t December
January to December inclusivo, and snow
January to May Inclusive, and snow
.June to October iucluslvo
35.20
855,092,800
383,986,420
. 419
303,300,400
210,044,479
.062
429,501,600
105,708,205
.246
' ShowH the (luatitUy of vvatef fiirnislied by the hiiiiw om the grouud tvlicu llio gauging comnioiiceil.
t With nieUiiig snow. (: Draiu.Tgo cqii.alized by roservoir,
4 A
2 G
104. TIio forogoiii«'' aro tlieonly tables of observations of tliekind tliat I liaveiiiet
with. Tliey oxbibit, in a striking,'' def^Tee, tlie remark previously made that .greater
(piantities of Avater can be collected in a cold than in a warm climate, or in a climate
having a longer winter or a greater number of months, with the ground so frozen as
to lessen the liltration.
105. On examining the first table, we hnd that, dnnng the months of Xovendjcr
and December, the whole (piantity of falling wati.-r could have been collected to Avithin
two-hundredths. It is also evident, from the second table, that the month of IMay
must be taken as the latest of the months allected bv the winter-collection. The drain-
age of this month and the one iweceding exceeds the falling Avater of both months;
the latter must therefore, evidently,'owe its great drainage to the accunudated ch'posUe
of the Avinter. These facts justify us in placing, for the summer-drainage of that cli¬
mate, or for the draiuage-jteriod in Avhich the (Irjmltcs and other effects of AA'inter are
not felt, only the months of June, July, August, September, ami October, liy the
finst table, the aA'crage drainage of these fiA'e months is 31.5 per cent.; and, by the
second, aA'crage drainage for the same month is 2d.G j)er cent.
1ÜG. Then, taking the tAvo Avinter-months of the first table, the average drainage
is 98.9 per cent. ; and, again, using the same Avinter-months of the second table, avo
have an aA'cragc drainage of 75 per cent.
107. Although Ave feel bound to say that these tables are too limited to justify the
establishing of any general rule, and that for such a purpose obseiwations extending
through many years, Avith the most exact measurements, can alone justify such a
course; yet, at the same time, Ave must acknoAvledge the facts tobe highly interesting,
and deserving the confidence duo to such limited observations from the just eminence
of the engineer under aaJioso directions they aa'cre made.
108. There is another remark due to the subject. The a'alley of a stream is not
only the drain of the quantity of doAA'ufall-aa'ater Avhich runs into it from the sur¬
face, but also of that proportion aa-hich, filtrating through the soil, finds its outlet in
the bed of the stream. A deep valley, therefore, must alAAmys collecta greater pro¬
portion of doAA'nfall-aa'ater than a shoal one, although the extent of drainage be the
same, as more is caught by filtration before it passes beloAv the bed of the Amlley.
Hence, the depth of the a'alley, in comparison Avith the edge of the drained basin, be¬
comes an essential element in such a question. Nor can the running Avaterof a stream
be included in the result of drainage, because the stream itself is the result of the
drainage ; and to calculate the stream and the drainage also is to iiiAmlve the same
quantity tAAÙce. It is only, therefore, at points Avhere streams come in beyond the limit
of the basin of aa'hich the drainage is included that quantities discharged by streams
can be included in or added to the quantity of AAmter obtained.
109. We have found that, in the first table, the drainage per summer-month Avas
less than one-third; and, by the second table, during the same period, rather less than
one-fourth. Then, taking the tAvo Avinter-months of the first table, or all the Avinter-
months of the second, the mean exceeds these proportions.
110. The tables of Mr. Jervis, therefore, plainly indicate a difference in the quan¬
tities collected during the summer and aa-intcr montlis; they, also, CAddently show that
27
seven months of the year is the nnmher in -which the quantity collected may be con¬
sidered as influenced by the winter-condition of the soil for the climate in which tlie
observations were made. For the climate in which the canal is situated that is to be
the subject of our report, if we were to allow four months as the number influenced bj^
the conditions of winter, we presume that we will meet the case rather above than
below its reality.
111. Before we go farther, it will be proper to consider the rate of rain to be
accepted. Through the politeness of my friend. Dr. Flarlan, of Philadelphia, I have
been supplied with an extensive collection of rain-tables for various parts of the coun¬
try; but, after giving to these the most deliberate consideration, I have come to the
conclusion that the most appropriate table for our subject is the one nearest the locality
of the contemplated canal, which is that of Mr. Brantz, of Baltimore.
112. The usual method of taking the average of several years' rain does not
appear to me deserving of imitation, because it is well known to every engineer that,
during abundant years, a vast amount of water is allowed to run to waste ; that is, is
discharged by waste-gates from the reservoirs. To introduce this in the average of
quantities collected Avould be to introduce a quantity never preserved, never applied
to any of the uses of the canal, and Avhich must therefore lead to erroneous conclusions.
It Avas probably OAA'ing to similar reflections that the board of engineers, in their report
on the Chesapeake and Ohio Canal, used only from Mr. Brantz's tables the rain of
1822. Under these considerations, Ave shall adopt for oiir object the rain of 1822 of
Brantz's tables; but, that those Avho differ Avith us on this point may liaA'O the means
of calculation on a different bqsis, Ave giA'c the entire table for nine years.
113. Talle of ike monilthj clejpth, in inches, of rain at Baltimore.
[From Mr. Brantz's tablos.J
Montbs.
1817.
1818.
1819.
1820.
1821.
1822.
1823.
1624.
Mean.
January
2.25
0.90
0.70
2.80
3.30
1.80
5. GO
2.30
2.85
February
2.80
2.00
1.90
2.20
5.40
4.80
0.70
5.90
3.225
Marcb
. 4.50
3.00
4.55
3.30
1.70
1.30
7.10
4.30
3.71
April
1.50
2.10
2.70
1.10
2.10
2.10
1.80
4.70
2.20
May
2.00
6.45
4.10
4.40
5.10
1.50
2.10
2.95
3.05
June
9.10
1.15
1.30
4. GO
1.80
1.50
l.CO
5.03
3.06
July
3.50
4.10
2.20
2.20
7.50
4.35
3. CO
3.37
3.85
August
10.40
2.00
4.30
8.00
0.30
0.80
4.10
4.50
4.30
September.....
3.30
3.20
3.00
1.50
10.70
2.25
5.80
2.94
4. 45
October
1.80
3.10
0.70
7.80
3. 40
2.50
2.80
1.77
2.975
November
3.70
2.00
1.10
2.70
5. GO
5.10
3.10
2.27
3.20
December
3. GO
2. CO
2.20
1.90
3.30
1.20
G. 25
2.25
2.90
Amount
48.55
32. GO
23.75
42.50
50.20
29.20
44.55
42.28
39.89
114. By the foregoing table it appears that in 1822 the fall of rain Avas equal to
29.2 inches, say 29 inches, Avhich Avould give for one acre 3,898 cubic yards. We haA-e
before remarked that the general opinion among engineers isthat one-third of the
doAvnfall-Avater can be collected; but, by the tables of Mr. Jcrvis, about tAvo-flfths can
íís
])0 collected, and, in Iiis opinion, two-íií'tlis may Lo countod on with safety. The ])oint,
tliorefore, njion wliioh one's jiido-mcnt may liesitate, is in tlie adoption of one-tliinl or
two-fiftiis. We acknowledfje tliat the facts in ifr. Jervis's tables liave more weight
with lis than conjecture. It is only that his observations were of so limited a period,
and that the excessive drainage of some montlis induces us to suspect error in the
observations, that wo do not at once adojit them ; as, for instance, table 2—while the
drainage of February and j\farch exceeds the ivliolo downfall-water of these two
months, that of April and IVfay, immediately succeeding, nearly ecpials the downfall-water
of those two months; the drainage of these four months exceeds the downfall of the
four; and the downfall of the two or three preceding months is not, taking the months
of the .same year as stated, so exce.ssive beyond the drainage satisfactorily to account
for it, with a reasonable allowance for evaporation and filtration. There may he no
error; the iiicts may he as stated; hut being very singular, and certainly new, we do
not think they would justify the adoption of a general rule until verified by repeated
subsequent observations. Now, excessive drainages are involved in the average
result of both tables, which in No. 1 is 0.302, and in Xo. 2 is 0.449, the mean of which
is 0.4205, or say two-fifths. Treating the table of îlr. llrantz for 1822 according to
our reasoning about suinmer and winter months, allowing four for the latter, the result
would also he about two-fifths, or 40^per cent.
115. But, from the remarks which ive have made on the tables of ]\fr. Jervis, ive
feel unwilling at present to adopt what they would justify. Observations are now being
made, in reference to the same subject, on the summit-pass of the Chesapeake and
Ohio Canal. These will probably confirm !JIr. Jervis's results, or, in conjunction ivith
them, furnish the profession with more positive data than it has hitherto possessed in
reference to this highly interesting question. Until then we feel some doubt about the
pi'opriety of deviating from the rule hitherto generali}- received, that one-third, or 33
per cent., of doAvnfall-water can he collected in well-arranged reservoirs, ilr. Jervis's
tables would justify the assumption of two-fifths, or 40 per cent. After all, the differ¬
ence between the two is no more than seven-hundredths.
IIG. Applying the rule, then, which ivo have decided to adopt, viz, one-third of
the downfall to the rate of rain of 1822, it ivill give, as the quantity which can be
drained into a reservoir from each acre of its basin, 1,299 cubic yards.
117. The next question refers to the loss which water experiences from evapora¬
tion and filtration after having been collected into reservoirs. Sutcliff, on this subject,
and referring to the reservoirs of the Eochdale Canal, says, " In the summer-months,
they sink one inch per day when the cocks are shut close ; and yet I think no reser¬
voirs are more water-tight than they. But I will only estimate upon the reservoirs
wasting half an inch per day, and confine it to those on Blackstonedge, as that at Hol-
Jingsíviork gives a certain-quantity of water constantIy_t(Lthe_mill-owners. wliich makes
it difficult to ascertain how much it wastes," &c. It is reaUy to beregrettecTtHaFIIns"
question had not been more nicely detennined, the opportunity being very favorable^
as the quantity which the mills consume admits of accurate calculation. We must,
however, under the circumstances of the case, be content with his rate of loss of half
an inch per day, or fifteen inches per month.
29
118. For the saiue object, Andreoisi appKes to the reservoh-s of the Languedoc
Canal twelve millimeters per day, equivalent to-0.472 of an inch. Tlie coincidence
between the two ia sufficient to justify us in adopting for the reservoirs a loss of lialf
an inch per day. These rates are given by both authora as actual states of loss from
exposed sur&ces under the effect of rain upon them.
119. We have collected much information upon resen-oira in our own country ;
but it was not of a kind, either in the character of its facts or their accuracy, to be of
use in the points which we have been discussing, and a reference to it would, in conse¬
quence, merely extend the volume of our report without elucidating its object.
120. Having concluded that an average rate of one-third of the downfall-water
can be collected into suitably-arranged reservoirs ; having shown that the drainage
betwœn winter and summer montlis varies considerably ; and having also decided that
for the climate of the contemplated canal foiu* months may bo assumed as the number
affected by the condition of winter, it now becomes necessary to ascertain the effect of
these considerations upon tlie rain assumed.
121. By the second table of Mr. Jervis, which extends through tlie whole niunber
of months in the year, it appears tliat the gunmier^ärainage was equal to 0.24G, say
0.25, or one-fourth of the downfall-water. Appljnng this quantity to eight summer-
months, and involving the remaining four for the balance of the remaining average of
one-third, it will justify for these latter (the winter-months) an amount of drainage
equivalent to 50 per cent, of the downfeU-ivatei-, rather more than the correct fr*actional
quantity. Now, applying these considerations to Brmitz's tables for 1822, we have the
following results :
îlouUia.
Fall of
Braiiieil.
Qúantity
Quantity drained
■water.
dcafueA.
pet aqnare aere.
Inches^
Per cmt.
InAm.
CiMe feet.
Jaanary,.
1.8
0.50
0.0
3207.0
Febrnary
4.8
0.50
2.4
8712.0
March
1.3
0.50
0,05
23iffl.6
April
2.1
0.28
0.525
1005.7
May
1.5
0.25
0.375
1301.2
Jbbb
1.5
o.m
0,375
isola
Jnly
4.35
0.25
1.0875
3047.6
Angnst
0.8
O.iT»
0.2
720.0
Septemher
2.25
0.25
O.IWÍ
2041.0
October i
2,5
0.25
0.025
2208.8
Hoyemhet
5.1
0.25
1.275
4028.2
Diicomber
1.2
0.50
0.6
2178.0
Total
20.2
0.333
0.575
34757.1
122. The total quantity which, by tlie foregoing table, may be collected in one year
from one acre, is IÍ4757.1 cubic feet, or 1287.3 cubic ysurds; and of this quantity it
appears that, during the four months of December, January, February, and March,
there may bo collected IGölG.ö cubic foot, or G11.72 cubic yai-ds ; and during tho sum¬
mer-months of April, May, June, July, August, September, October, and November,
30
18240.G cubic feet, or (!7D.r»7 cubic yards. From Avliicb it will bo perceived that tbo
four juontbs of Avintor-drainajpa, being nearly equal to tbo wbole drainage of tbe eight
É^umnier-niontlis, mIioavs the necessity of so planning and aritinging the reservoirs that
the Avintcr-drainage may be collected and preserved to meet the deficiencies of tbe
Ruminer-snpply.
123. These remarks naturally lead us into considerations of the dimensions of the
reservoirs, a matter, hoAVOA'er, Avhich more properly belongs to the idfiu of the canal
after its practicability has been determined. Ilut, generally speaking, tlicso dimensions
sbould be adopted to fill the canal on the opening of navigation, and to maintain its
trade and aa-aste by supplying any deficiency from the summer-drainage and iirobable
drought.
124. The dimensions of reservoirs have great influence upon their usefulness.
Deep and naiTOAA* a-alleys should always bo selected for such purposes. The losses
they experience are in jiroportion to the surface ; the loss the exposed surface in Avhich
the same quantity of Avater can be confined the bettor. The reader aa'ÍII the more
readily appreciate this remark Avhen ho understands that the surface of one mile square
is sixteen times as great as a surñice of one-quarter of a mile square ; and if, therefore,
by the fortunate position of a narroAV and deep a'alley, a reser\-oir could be constructed
that should not expose moro than a quarter of a mile square of surface, and contain
as much as under other circumstances Avould have to be spread over one mile square,
the same mass of AA-ater aa-ouUI in the one ca.se lose onh" one-.sixteenth of Avhat it Avould
•/
in the other. From Avhich it may also bo inferred that, from the Avant of suitable posi¬
tions for reserA'oirs, a canal may be impracticable, although the extent of surface drained
Avould yield a sufficiency of AA-ater.
125. Dimensions.—As the contemplated canal i.s, in fact, an extension of the
Chesapeake and Ohio Canal to Baltimore, Avhich Avould make that city one of its great
tei-minationa on naA'igable aa-aters, it ajipeai-s to me there can bo but one opinion in
reference to its dimensions, trunk, and locks ; and tluit these should be the same as those
of the canal of aa'hich it forms so important a part. But, in consequence of the ncAV simi-
mit to this part, the lift of the locks may be reduced, in order to adapt them the better
to the probable supply of A\ atcr. Such, alsoj appears to bo the opinion of Engiueei-s
Trimble, Fisk, and Hughes. The first adopts a lift of 5, the tAvo others of 4^- feet.
Preferring of the tAvo, the lift of 5 feet, wo shall assume that in our calculations.
Accordingly, therefore, our reasoning aaùII be applied to a canal 60 feet at aa-ater-sm-
face, 82 feet at bottom, and 6 feet deep; to locks 100 feet by 15, with a lift of 5 feet,
the prism of lift of which Avill be 7,500 cubic feet, equal to 2,77.7 cubic yards. In
adopting, hoAvever, this reduced lift, it is solely from the consideration that it may be
necessary in order to accommodate the canal to the supply of aa-ater ; experience hua--
ing proved that, in most points of A-iew, the best lift for a lock is from 7 to 8 feet.
126. PractîcaMîti/.—The question of practicability, AAÛth due supply of AAmter,
depends upon the quantum of trade. A canal may be made, and there may be Avater
enough to fill it ; but if thei-e should not be enough to sustain a reasonable degree of
trade, we belieA-e the common sense of mankind would at once decide that such a canal
was impracticable.
127. For thé probable extent of this trade, Ave will refer to the extremely interest¬
ing remarks, nnder the head of " General considerations," in the rejiort of the board of
engineers upon the Chesapeake and Ohio Canal ; and a slight degree of observation
upon the facts daily developing is sufficient to demonstrate that the vdews of the board
will soon be reahzed. These, however, embrace the great trade east and Avest, in
Avliich this canal cannot participate until the great communication is completed ; but,
whenever completed, the extension to Baltimore must come in for a share. Its prac¬
ticability, therefore, should have reference to its capability.
128. But, although ¡participation in the great trade to the West may not soon be
realized, yet Ave knoAV that the line to the great mineral-region of the Alleghanies is
now within a year or tAA'O of being completed, and that it will be in full operation by
the time the contemplated extension to Baltimore can be made. This extension will,
therefore, liaA^e in the outset to SAibserve an extensive and established trade ; in refer¬
ence to Avhich, its capability should be tried.
129. The Alleghany is the great bituminous-coal region of our country AAuth AAdiich
this canal has to communicate. It AAmuld be superfluous to reason upon the amount
of trade from such a region. Our periodicals are full of facts upon the subject, Avith
aa'-hich every one Avho can read has already become acquainted. That the demand for
tills mineral aaóII soon bring the canal to the maximum of its capability no one can
doubt ; and, using that principle as data, Ave may determine its practicability Avith due
supply of water. The maximum of the ability of a canal depends upon the number
of boats Avhich can be passed through its locks. A medium, Ave shall place at half that
number ; a minimum, at one-fourth ; and, in our judgment, the c.anal Avhich does not
possess a minimum ability is impracticable. Our remarks have no reference to profits.
We Avill admit at once that a minimum ability Avould not furnish a profitable income
upon the investment ; that it Avould be a mere barren ¡)racticability ; but there may be
cases in Avhich it Avould be to the advantage of the State to construct a canal, there
being no other route practicable, regardless of any probability of profit from its rev¬
enue. This is a matter for the State to decide. I have to do only Avith the question
of "practicability, Avith duo supply of Avater."
130. Bare barren practicability, then, might be considered as possessed by a canal
Avhich could supply with its Avater all causes of Avaste, and be able to sustain a mini¬
mum trade. Bare practicability is not, hoAvever, the question to be decided ; it is "prac¬
ticability, Avith a due supply of aa'ater." "Duo supply" can liave no other meaning
than "adequate supply," and adequate supply mxist have reference to the probabilities
of trade. If avo suppose, then, that the commercial advantages of Baltimore Avould
enable her to direct about one-half of the entire trade of the Chesapeake and Ohio Canal
to her oaa'n stores—and Avithout doubt the object of the canal is to gi\m Baltimore all that
it can command of its trade—it Avill then be necessary to shoAV tluvt the canal aaùII be
able to pa,ss at least that quantity, or avo shall fail in proving an adequate siqqfly of
Avater. The point, then, of "practicability, Avith duo supply of Avator," depends upon
the question Avhethcr or not the supply Avill be adequate to Avhat avo have proAÙously
distinguished as a medium trade, or half the entire poAvcr of the locks Avith a fidl sup-
¡)ly of Avater. Half the num1)cr of ¡¡assagcs of a full siqqfly Avill, therefore, be taken
32
ils tlie test of " priietieiiLility, Avitli due siijijdy iuid if it slioidd iippeîir tliiit tliere is
AViitor enough for sucli a number of passnges, adding thereto allowances for waste, T
shall not hesitate to give it as my opinion that the canal "is ¡iracíicable, with a due
supply of- Avater."
131. Now, wo will sujipose that 12 boats ])er hour may be, passed through a lock
of 5-foot lift, and that the average daylight during the ten months of navigation is 12
hours. As there is ii lock at each extremity of the summit-level, there would be 24
passages per hour, or 288 per day, for the maximum ability of the e.xtension to Haiti-
more. A medium ability, or that which I have considered " practicable, Avith due
supi)ly of water," would then bo 144 passages both Avays, or 72 ¡lassages each Avay.
A7e Avill, hoAvever, for greater security and for facility of calculation, assume 80 pas¬
sages each Avay per day. The engineers aa Iio have previously reported on this matter
liaA-o as.sumed 100 passages each Avay; in taking but 80 for our guide, avo may be-con¬
sidered as treating the (piestion Avith great liberality. Our reader Avill bear in mind
that Ave assume 80 passages per day as no more than half the ability of a lock of 5-foot
lift, Avith a full sup[)ly of aa'ater, and that aa'C consider it necessary to shoAv Avater enougli
for this number of passages in each direction, or IGO in the two directions, or a\*e shall
fail in proving the "practicability of the canal, Avith due siqi^ily of Avater," and aa'hich
Ave have said should depend upon its ability to direct about one-half (rather more) of
the trade of the Chesapeake and Ohio Canal to Haltimore; aa'hich trade aa-e have con¬
sidered equivalent, or that it Avill be, to the full abilit}' of its lock for tAveh'c hours.
132. AVe have noAV terminated our remarks upon AA'hat aa'o consider the prelimi¬
nary questions of the case. They liaA-e extended themseh'es, hoAVCA'cr, into greater
length than Ave had anticipated. We .shall therefore endeaA'or to generalize them, and
to reduce them, so that their application Avill be more couA-enient.
133. AVe haA'c .shoAvn that the Languedoc Canal, during ten month,s of navigation,
loses by its filtration more than eight times its prism of Avater. It Avill not, Ave belicA-e,
be considered unreasonable to suppose that the pi'ism Avhich the öanal contains at the
closing of its navigation is lost during the remaining tivo months, and, of consequence,
on the opening of naA'igation, this prism has to be supplied from the feeders, aa'hich aa'ÍII
make more than nine prisms of aa'ater for the ten months of naA'igation. To this item
must yet be added the losses from oA'aporation and the leakage from the locks.
134. AA'^ith such facts, Ave presume the inference aa'ÍII not be di.sputed that this canal,
the one aa'hich loses the least from all causes of Avaste of any knoAA'ii canal, cannot lose
less, during its ten months of naA'igation, than ten prisms of Avater, or one prism per
month.
135. But Avould it be aa'ise to adopt as an estimate for another canal the losses
Avhich one of the character of this experiences ? AA'^e should ansAver in the negath'e.
MoreoA'er, if our vieAvs of its eA-aporatioiybe correct, as preA-iously explained, (25,) to the
nine prisms stated (in 133) as its loss from evaporation should be added three and one-
fifth prisms. Then, if Ave suppose the leakage from the lock-gates, and all other causes
of aa'aste, merely adequate to make up this last fraction, the whole aa'ÍII gh'e, for its
total loss from all causes, tliirteen prisms of "la'ater for its ten months of navigation, of
one and three-tenths of a prism per month. AA'^e liaA'e seen (44) that the cube of this
33
canal, for one mile, is 64,207 yards, wliicli, treated for the losses we liaye just enum¬
erated, will make the same equal to 52.2 cubic feet per mile per minute, which, in our
judgment, is not beyond the reality. The evident disposition in all the authorities to
which ave have referred to a'aunt the advantages and lessen the defects of this canal is
continually invohdng the latter in minimum considerations, and, consequently, unsafe
I'ules.
136. The board of United States engineers, in their report on the Chesapeake and
Ohio Canal, supposed the losses from filtration and evaporation Avill be one prism per
month—less than Avhat Ave have already seen actually takes place Avith the Languedoc
Canal. The opinion of the board appears to have been founded upon observation in
reference to the Narbonne Canal, AAdiich, after a use of six years, lost one and tAvo-thirds
of its prism of AAmter ; and, considering the summit of Avhich they Avere treating, (more
tenacious in its soil than that of the Narbonne Canal,) the inference draAvn Avas that-the
former AAmuld lose once its prism per month.
137. The Narbonne Canal may be supposed to have reached its minimum loss in
six years, and the rates given are for filtration and evaporation only ; that of leakage
at lock-gates is not taken into the account. Nor is there in our canals that care of con¬
struction and extent of excellence in puddling, aa'hich the board evidently took into
consideration in the estimate of loss of Avater Avliich they gave.
138. Moreover, in the second report on the same canal, (page 54,) the board,
reasoning upon a different sumuAit, much more abundantly supplied aa'ith Avater than
that taken into consideration in the first report—not requiring so close a calculation to
shoAV its bare practicability, and Avhich they recommend to be adopted in preference to
the first—-take great pains to shoAv that there Avill be 120,000 cubic yards per mile per
month for the Amrious causes of loss, exclusive of lockage. Noaa', as the prism of the
canal of AAdiich they Avere treating is nomorethan 39,785 cubic yards in a mile, avc see
that the summit Avhich they ultimately and unequivocally recommend, and for AAdiich
they furnished a plan and estimated the cost, had a supply of Avater, exclusive of lock¬
age, of betAveen three and four times its prism per month, " destined [as the board thein-
sehms express it] to feed the canal, exclusive of lockage,'' or, in other Avords, to supply
Avater for. all other causes of consumption.
139. xilso, in the general opinion given in the first rejiort of the loss of one canal-
prism of Avater for each month of navigation, consideration docs not appear to have been
given to the prism left in the canal, and lost Avhile' the navigation is suspended, or for
the lock-gate leakage.
140. On these accounts, Ave cannot forbear expressing it as our. opinion that an
alloAvance of one prism of Avater per niontli of navigation, for all causes of exhaustion
except lockage, Avill prove to bo insufiicient, and is, therefore, an unsafe rule.
141. The loss on the Erie Canal, Avhich avc have foAind, at the least of the ascer¬
tained rates, to exceed five times its prism per month, is, Avithout doubt, singularly great.
The observations Avere made in 1834, Avhen its losses should have approached a mini¬
mum. It Avould be considered out of ])hice to discuss, in this report, the probable
causes of so great a loss of Avater ; nor have Ave, in fact, that accurate knoAvledgo of
the canal Avhich Avould justify the attempt; ])ut, as a mere opinion, avo feel disposed to
5A.
34
pliUHî inudi to tito ¡iccoiiut of (Icfcictiveuoss in tlio original coii.stniotion. iîo that aw it
may, liowcvor, wo slioiild not licsitato to pronoiuico a canal as practicahle tliat shonhl
pofisoss a loss supply ; nor shonhl wo feel ourselves as doing jnstico to the profession of
the engineer if we were to re(piire resources of Avater to equal the standard of the Erie
Canal before Ave aa-oidd gía'e an opinion in faA-or of their suiliciency.
14'2. The loss for liltration and e\-aporation on the Chesapeake and Ohio Canal
has been found to be about tAvico its prism of Avater per month of navigation. Xoaa',
as this canal is the same in its dimensions as that to Avhich our remarks are to be applied,
the climate also similar, and in some degree its soil, Ave consider it the Í!AÍrest guide
for our opinion, and shall therefore adopt the results it has yielded.
143. Our roa.soning, then, Avill furni.sh the folloAving data for calcnhiting the quan¬
tity of aa'ater that Avill be exhausted :
1st. The canal has to be fdled.
✓
2d. TavoIvo lockfuls per day should be alloAved for the leakage of each lock at the
end of the summit-le\'el.*
3d. Tavo prisms "of the canal per month for losses from liltration, absorption, and
evaporation.
4th. Taa'O lockfuls of aa'ater per boat for the pas.sage of the summit.
r)th. Taa'C'Ivo and a half prisms of the feeders per month for loss in feeders.
I feel loss confidence in the adequacy of this than of any other item. It is taken
from the experience of the Languedoc Canal, in Avhicli particular care has been be-
stOAved upon the construction of the feeders. I desire it, therefore, to be di.stinctly
understood that I contemplate Avell-constructed feeders, carefully puddled throughout.
Gth. One-third of the doAvniirll-Avater as the quantity aa'IucIi can be collected in the
reservoirs.
7th. To alloAV a loss of half an inch in depth for each day for the Avater Avhen col¬
lected. The loss on this account Avill extend through the aa'hole year.
8th. And, for the locality of the canal in contemplation, to adopt a rate of rain of
29 inches per year.
144. But, after all, eA-ery candid and exjierienced engineer must acknoAA'ledge that
these rates can be a'icAved only as a minimum'; less Avould be inadequate to the object.
Any unforeseen event, therefore, that creates additional loss at once throAvs the supply
into a state of inadequacy, and produces a comparative failure in the canal. On these
accounts, it is the duty of OA^ery engineer, after liaA'ing stated all the causes that can be
appreciated AA'hich consume Avater, to sIioav a proper surplus to meet unforeseen con¬
tingencies.
145. In matters admitting of much greater accuracy, because founded on more
correct data—for instance, the expenses of constructing the canal—does not every
engineer, after having included ca-ery item Avhich experience has suggested, then add
his 12 or 15 per cent, for accidents and unforeseen contingencies ! Yet, in a matter of
that kind, the error of a short estimate involves no greater evil than the expending of more
money than had been at first contemplated. But, in the Avater for a canal, the error
for a short estimate may probabl}' make the Avhole expenditure of money useless. IIoav
nrucli more important it is, then, that surplus Avater should be at command. The reflec-
"Annalcs cles pouts et clíaiissées, vol. 10, p. 162.—Eight lockfuls per day are allowed for losses ou this accouut.
35
tion becomes of greater weight when we bear in mind that, in every instance, the water
consmned by canals has exceeded the amontit anticipated. Even after the long-con¬
sidered and most cautiously-pnrsued measures in reference to the Languedoc Canal,
the additional reservoir of Lampey had to be added.
146. The engineer should, therefore, show that his arrangements will procure a
large surplus of Avater, or that a surplus is at command, by additional and appropriate
arrangements, should it be required.
147. Having now completed the preliminary remarks, Avhich appeared to me to"
be essential to a correct understanding of the subject, I shall proceed to apply them to
the particular cases of the survey.
148. For the reasons alreacly given, (4,) the field-operations Avere at first confined
to tAvo routes, namely, the Linganore and the Seneca routes. These Avere the tAvo upon
Avhich reports had already been made, and in reference to Avhich the executrte of
Maryland had founded a decision upon their " practicability, Avith due supply of Avatcr."
No other survey south of these, and exclusively Avithin the limit of the State of Mary¬
land, had then been made ; and the impression AA'as general that no pass existed south
of these, and Avithin the limits specified, the characteristics of AAdiich Avoidd Avary in
adA'antages o^'er those Avhich had been previously surveyed. But, from a knoAvledge
of the country acquired by a summer's residence there, I Avas indiiced to entertain
doubts of the correctness of tins impression, and accordingly directed the engineers
that, in addition to the reneAved surveys of the routes in question, they should also
carefully examine the ridge of high land elseAvhere, and determine positiA'ely Avhethcr
or not any better Avay of passing it existed. The result exceeded my expectations. I
AAms early infomied by Mr. KirkAvood that a route existed passing the ridge a feAv miles
south of the fonner surveys, and much loAver. lie Avas required to bestoAv his best atten¬
tion upon it. We Avere thus involved in the survey of three distinct lines, instead of
tAvo, as had been at first contemplated. In fact, it may be said that four lines Avere
surveyed, as the data for tAvo suppositions of the original Seneca route Avere collected.
149. I had also requii-ed the engineers to limit their operations to Avhat might be
considered the summit-section of each route, by Avhich I mean that section Avhich Avould
receive its supply of Avater from the summit, and Avhich includes the summit-level, and
the extension of the canal each Avay, to points at Avhi'ch ample secondary siqiplies Avoxild
be received. By this plan, all the debatable ground AA^as coA'èred ; and, by tlius limit¬
ing the field-AA'ork, it Avouldbe terminated soon enough to make a report upon the point
of principal interest—in fact, upon the sole point iiiA'olved by the resolutions of tlie
legislatiu'e—in the time anticipated by the legislature. Had the field-AA'ork been
extended this season to tlie canal on one side, and the city of Baltimore on-the other,
it Avould have been a mere repetition of matter upon Avhich no diflerence of opinion
exists in reference to the practicability,of the route ; and AA'hicii, from the delay it Avould
have occasioned, Avould ¡¡robably have put it out of my poAver to have made a report
in time for any action of the legislature at its next session.
150. Of the three lines mentioned, I shall give but a summary description, refer¬
ring for a more detailed knoAvledge of them to the joint report of the engineers, Kirk-
Avood and Lee, hercAvith appended, and from Avhich the folloAving facts are taken. The
map attached to this report Avill enable tlie descriptions to bo the better understood.
ti(\
THE LlNOANOliJC IÍOUTI':.
151. Tliis route passes tlie ridg-e tlinrngli the valleys of ]\Ii(l(lle Iltui and Grimes's
Spring llrancli. Its sunnnlt is il3G,07G feet helon' the ridge at Grimes's tobacco-lionse,
and 530,1'i 9 feet above tide, aecording to tlie survey made by the engineer, J. Trimble,
d'lie length of the summit-section is 12 miles 714 yards, and it will first derive its
secondary supplies of water from the Patapsco on the one side, and from Talbot's Ilranch
on the other. It Avould recpiire a tunnel 3 miles 157 yards long, and will command a
drainage of 2G.9S stpiare miles. It will admit of an arrangement of three reservoirs,
namely: First, one on Gillies's Falls, with a dam 48 feet high, a surface of 71.81
acres, containing 3,475,470 cubic yards of Avater, and receiving the drainage of
11,202.7 acres; second, one on Warner's Ilranch, AAÎth a dam 38 feet high, a surface
of 26.24 acres, containing 1,072,05G cubic yards of Avater, and receiving the drainage
of 3,346.447 acres; third, one on Ik;a\'er Dam, Avith a dam 40 feet high, a surface
of 20.707 acres, containing 850,851 culnc yards of Awater, and receiA'ing a drainage of
2,718.89 acres. It will also require three feeder-lines; in all, 3,437 yards long.
152. The total quantity of surface drained being 17,268.05 acres, at the rate of
25 inches of rain, and, siq)posing one-third to be collected, it Avill yield 22,441,354
cxAbic yards of Avater, Avhich is the extent of the supply Avhich can be commanded for
the summit-section of this route. We aa'íII uoav ascertain its adecpiacy to the Avants of
the canal.
153. There Avill be required—
Cubic yards.
1. To fill the canal GG9, 575. 96
2. For lock-leakage 1,959, 995. 00
3. For filtration and CA-aporation 13, 391, 519. 20
4. For the trade of the canal 26, 666, 640. 00
5. Loss in feeders 1, 432, 183. 725
6. Loss from reserA'oirs 1, 896, 180. 000
Total quantity required 46, 056, 093. 885
Total quantity aA'ailable 22, 441, 394. 298
Deficiency 23,614,699.587
154. This route is, therefore, impracticable. It Avill be seen that the supply is
eA'en inadequate to the Avants of the locks for the trade, exclusive of CA-ery other con¬
sideration.
THE SENECA ROUTE.
155. The course of the survey led to tAvo siuweys in reference to a part of this
route, A'arying its termination in the A-alley of the Seneca.
First case.—It will require a tunnel 547.66 yards long ; the suinmit-leA*el Avill pass
122.47 feet beloAV the ridge at II. Griffith's ; Avill bo 41.26 feet above the Patuxent
37
Hiver, at Etcliinson's Mill; and will be 496.26 feet above tide, according to tlie data of
the engineer's (Trimble) survey. Our operations, as before remarked, not extending,
in any route, to the termini of the canal, Ave bave to avail ouraelves of tlie labor of
our predecessors, in order to ascertain the reference to tide-Avater.
The secondary supjilies Avill be derived from the Wild-Cat Branch of the Seneca,
and the Seneca itself, as the canal progresses, on one side; and the Cat-Tail Branch of
the Patuxent, the Patuxent itself, &c., on the other. The total ^length of the summit-
section will be 14 miles 1,193 J yards. It admits of the arrangement of two reseiwoirs
First. On Cabin Branch, witli a dam 30 feet high, with a surface of 31.253 acres,
containing 1,008,420 cubic yards, and having the dminage from 2,903.68 aa*es.
Second. On the Patuxent, Avith a dam 42 feet Mgh, with a surface of 58.05 acres,
containing 2,622,312 cubic yards, and having a drainage from 8,452.080 acres. The
feeders fi-om these reservoirs will be 2,485 yards long.
156. The total quantity of smface drained being 11,445.76 acres, it Avould yield,
at the rates stated, (152,) 14,875,247.7 cixbic jTU-ds of water for the available supply
of this route.
157. The demands for water aauII be—
Cnbic yards.
1. To fill the canal 792,211.971
2. Lock-leakage . 1, 999, 995.
3. Filtration and ca'aporation - 15, 844, 239.
4. Canal-trade 26,666,640.
5. Loss from feeders •- 1, 763, 313. 250
6. Loss from reservoirs 1, 345, 095-
Total quantity required 48, 415, 494. 221
Total quantity aA^ailablo— 1 14, 875, 247. 700
Deficiency 33, 540, 246.521
158. This route is, therefore, impracticable. The available quantity amounts to
but little more than half the amount required for the locks, exclusivo of oveiy other
consideration.
150. Second cftse.—The summit-level in this is the siimo as in the first case ; the
secondaiy supplies also the same, Avith the difference that Darby's Branch is the first
used in the valley of the' Seneca. The reseiwoirs are also tlie same. The summit-
section is 11 miles 73J yards in length; the difference betAveen this and the summit-
section of the first case being the solo cause of difference in the demand of aa'ater
between the tAvo, it is not necessary to repeat the statement, in reference to Avater, in
detail, ■ .
Cubic yards.
The total quantity required is 44, 295,172.107
Total quantity available. 14, 875, 247. 700
Deficiency : 29, 414, 924.407
38
IGO. Tliis vouto is, tlioroibro, iDipracticuble ; and, as in tlio first case, it will be
pereoivcd that tlio (iniiiitity of avniiablo water is but little nu>re tlian balf tlio ijusiiitity
roiiuired for tlie moro uso of the locks in passinj^ tlio trade.
101. I have iiow applied tlie general rule.s which have been doterniined to the
])ecidiarltios of those lines which had been the sidyocts of previous report, and in
TOfcrcnco to which tho decision of tho esociitive of Jfaiyland had been given, that they
were impracticable in reference to duo su¡}pl}'- of -water. It ^vill be seen that I agree
with that opinion, and eonsider them imjn-aeticable also. AVliether I am right or wrong
is for others to decide. 1 believe myself to be right, and have fairly exposed all the
reasoning upon which my opinions are founded. Tho flicts to which my reasoning
lia.s been applied were not collected by myself, ns before rcmaihed, (8.) This duty
was committed to tho Engineers Kirkwood and Lee, and without interference beyond
general directions, and a roferoiicc to former reports on tho same subject. The prelim¬
inary observations which have governed my o]nuions were digested and written out
before the surveys were completed, and, of couwe, before I could bave any anticipa¬
tion of tho opinion tliey might induce in reference to these surveys. My object was
to establish certain general principles, and, being satisfied with their correctness, to
follow them out, no matter to what conclusions they might lead, or with whom they
might compel mo to differ. Iliffereneo of opinion with some one was inevitable, as
engineers of dosoiwedly great fame bad already given diametrically opposite opinions
on tho samo subject. With both, it was impossible to agi-eo. But such differences ore
not nnusnal. In matters which, like these, do not admit of mathematical precision,
they ore difficult to avoid. Wo find accounts of them in the works of foreign engineers,
and, therefore, the less suiiirising in our country, ^vhere a more limited experience has
done BO much less in settling rules for practical opei-atious. If I have had any advan¬
tages over those who have preceded me in this matter, it has been solely in tbe more
time at my disposal, and the greater means in my power to apply to the execution of
the surveys, Avhich have probably enabled me to collect more, and with gi-eater care,
the facts upon wliich an opinion can ho founded.
162. It was remarked (148) that three distinct lines had been surveyed. Having
reporfed upon two, it now remains to bring tbe pecidiarities of the third and last to
notice. We shall call this, by way of distinction, " the Brookville route," as it passes
near that villa^.
BROOKVILLE ROUTE.
163. The summit-section of this route is 16 imles 1,506| yards long, connecting,
on the one side, with the Seneca, at the mouth of Whetstone Branch, and on the other
with tlie Patuxent, at the mouth of Ilawling's River.. Refemng to a bencli-mark of
Mr. Trimble's survey, near Mr. GrriffitbV, iritli wliich the siuwey of this line was con¬
nected, its sumimt-level is 375 feet above mean tide, and 120 feet below what lias beeii
heretofore denominated "the Seneca route," and between 8 and 9 miles south of it.
The greater depression over any other surveyed route, by wliicb tliis line (the Breok-
rflle route) is made to pass tlie intervening ridges, gives to it gi-eat advantages, partic-
nlarly in reference to supplies of water. It will reiiuire two tunnels : one in passing the
39
Eockvillö Eidge, 2,800 yards long; and anotlier in passing tlio Meclianicsville Eidge,"
2,G00 yards long; after wMcli it enters the valley of Eeedy Branch, a tributary of
Handing's Elver. The total length of tunneling ndll, therefore, be 5,400 yards, or 3
miles 120 yards.
1G4. The line will admit of an arrangement of six reservoirs, viz:
First. One on the Seneca, with a dam 40 feet high, a surface of 152.GG acres, con¬
taining 4,214,955 cubic yards, and receiving the drainage from 10,908.16 scpiare acres.
Second. One on Goshen Branch, with a dam 20 feet high, a surface of 94.123
acres, containing 2,065,266 cxibic yards of water, and receiving the drainage from
4,613.12 square acres.
Third. One on Hawling's Eiver, xvith a dam 45 feet high, a surface of 96.648
acres, containing 2,548,450 cubic yards of water, and receiving the drainage from
6,515.2 square acres.
Fourth. One on the Eatuxent, with a dam 50 feet high, a surface of 336.685 acres,
containing 11,039,352 cubic yards of water, and receiving the drainage from 21,863.04
acres.
Fifth. One on Cat-Tail Branch, Avitli a dam 40 feet high, a surface of 331.382
acres, containing 7,444,741 cubic yards of aa'ater, and receiAung a drainage from 17,648
square acres.
Sixth. One on Big Branch, Avith a dam 30 feet high, a surface of 40.404 acres,
containing 900,463 cubic yards of Avater, and receiA'ing the drainage from 2,497.92
square acres. "
165. The dams in some of these reseiwoirs aaùII admit of being raised higher, if
necessary, so as to contain more Avater AAuthout any unfavorable extension of surface.
166. The total development of all tlie feeder-lines of the reseiwoirs amounts to
15 miles 903 yards. The feeders, hoAvever, so unite as to form but tAvo points of con¬
nection Avitli tlie summit-level.
167. The total extent of drained siuFxce being 64,045.44 acres, it aaùII yield at the
rate of 29 inches of rain, and, on the suposition that one-tliird of tlie same can be
collected, an amount of 83,229,611.09 cidjic yards of aAxailable aa'ater.
168. lYo Avill noAv see Avhat amount of Avater Avill be required, on tlie supposition
of ten months, or three hundred days, of navigation:
Cubic yards.
1. To fill tlie ciuial 909, 774. 500
2. Leakage at locks 1, 999, 995. 000
3. Filtration and evaporation 18,195, 490. 020
4. For the trade 26, 666, 666. 666
*■ 5. Loss from feeders 11, 376, 199. 999
6. Half an inch per day loss from reservoirs, for 365 days 17, 206, 399. OOO
Total required 76, 354, 523
Total quantity aA'ailable 83, 229, 611
Surplus 6, 875, 088
40
Kü). Tili) lîi'ookvillo roiito muy, tliCTcí'oro, luj proiiouiiuctl "practlculilo, with due
í^upply oí water." In tliis, us well us in the other euses, tlio rute of loss from tlic reser¬
voirs was not. up})lie(l to tlie muximum .surfuee wlien full, as ^iven in the preceding
description of the several routes, hut to a reduced avcra;^e surface, on the su])position
of a pro[)ortionato reduction of the water in the reservoirs from the use of the canal.
170. In the investigation of the pecnliarities of this route, some facts were col¬
lected leading to the prohahility that, from G to 8 miles still farther soutJ), a route
might bo ascertained that would reduce the tunnel-length. These facts developed
themselves oidy in the plotting of the experimental line.s, and at a time when it was
not possible to i)nrsue further investigations in the field, which would have rerpiired an
entire survey of a uoav lino, with an entire now arrangement of reservoirs and feeders,
and a survey of all their numerous details.
171. It will be .seen that I have limited my re¡)ort to the single (piestion involved
in the resolutions of the legislature—"jiracticability, with due snpjdy of water." An
estimate of ¡irobalile cost can be made, if desiralile.*
172. These .surveys having cost more than had been anticipated by m3'self, it is
jiroper that I should explain the causes of it. In the first place, it was not contemplated
that it would be necessary to survey au}- other than the Linganoreand Seneca routes;
but, in the prosecution of these, a third (the Brookville route) manifesting itself, and
with such advantages over either of the others, it was also surveyed. This last route
involved as many details, and as much labor nearh', as the other two; so that the actual
cost will be found not to have increased box'ond the original estimate more than in
proportion to the actual increase of labor Ijeyond what had at first been anticipated.
1713. In conclusion, I consider it a duty to acknowledge 1113' obligations and thanks
to ^lessrs. Kirkwood and Lee, the principal engineers under me, and to whom the sur-
vo3's were committed, for the intelligence, the zeal, the industiy, and econouy with
which their operations were characterized.-
Ilespectfull3' submitted.
J. J. ABERT.
December 10, 1838.
• The estimate is now being made.