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YALE UNIVERSITY
LIBRARY

From the Library of
ROBERT M. HOSLEY, Y 1900S
Gift of

HARRY P. HARRISON'ifal

ILLINOIS AND ST. LOUIS BRIDGE COMPANY.

REPORT

OP THE

CHIEF ENGINEER

OCTOBER, 1870.

ST. LOUIS:

MISSOURI DEMOCRAT BOOK AND JOB PRINTING HOUSE.

1871.

ROCK

ILLINOIS & ST. LOUIS BRIDGE

T. K	& C<> 13 William St N YILLINOIS AND ST. LOUIS BRIDGE COMPANY.

REPORT

OP THE

CHIEF ENGINEER.

OCTOBER, 1870.

ST. LOUIS:

MISSOURI DEMOCRAT BOOK AND JOB PRINTING HOUSE.

1871.CHIEF ENGINEER’S REPORT.

St. Louis, October 1, 1870.

To the President and Directors of the St. Louis and Illinois Bridge
Company:

Gentlemen : I have the honor to submit the following report:

THE AVEST ABUTMENT.

Tho masonry of the west abutment has been completed from
the bed-rock of the river to a point thirty-one feet above low-
water mark. From the bed-rock to the top of the masonry,
the height is now forty-four feet. Eight course's of granite are
laid on it, and two courses, or five feet, are required to complete
it to the skewbacks against which the steel ribs of the westorn
span will rest. This mass of solid masonry stands upon the lower
edge of the wharf in St. Louis, and measures at its base, in the
direction of the river current, ninety-four feet, and transversely
sixty-two feet nine inches, and contains at this time six thousand
three hundred and eighty cubic yards of masonry. When com-
pleted to the carriage-way, it will be one hundred and fifteen feet
high, abovo the bed-rock of the river, and will then contain eleven
thousand eight hundred and sixty cubic yards of masonry.

The work on it is going steadily forward in a satisfactory
manner.	'

Although the bed-rock at the site of this abutment is seventy-
three and a half feet higher than at the east pier, the difficulties
encountered in building its foundation were of a much more
perplexing and tedious character than those encountered at either
of the others. Its site had been for over sixty years a part of the
steamboat wharf of the city, and; as such, had received every kind
of useless material thrown overboard from the various steamers4

THE WEST ABUTMENT.

lying over it during that time. The old sheet-iron enveloping
their furnaces, worn-out grate-bars, old fire-bricks, parts of smoke-
stacks, stone-coal cinders and clinkers, and every manner of things
entering into the construction of a Mississippi steamer, seemed to
have found a resting-place at this spot, and constituted a deposit
averaging twelve feet in depth over the rock. During the memora-
ble fire of 1849, when twenty-nine steamers were destroyed at the
levee, the wrecks of two of them sunk upon the site of this abut-
ment. One of these was partly covered by the hull of the other,
which probably sun,k immediately afterwards. The lower one
was but two or three feet above the bed-rock. After this terrible
conflagration, the city authorities determined to widen the wharf.
Its front was extended to a line inclosing about one-half of these
two wrecks, by filling in with the stone and rubbish from the city.
During this extension, several other vessels were burnt at the
wharf, and the wreck of one of these also sunk upon the site of the
abutment. The coffer-dam, constructed to inclose the site, had to
be put down through these three wrecks, the hulk of either of which
was not probably less than four hundred tons measurement. Their
bottom planking was all of oak, three or four inches in thickness.
To drive the sheet-piling down through these hulks, an oak beam
six by ten inches square, armed with a huge steel chisel, was first
driven down as far as a steam pile-driver could force it. It was
then withdrawn and a sheet-pile, five by ten inches square, was
driven down in its place. The coffer-dam was formed of two
courses of sheet-piling, six feet apart, which were filled in between
with clay. When this was completed, $he water pumped out and
the excavation prosecuted within it, the discovery was made that
from one-third to one-half of the length of each of these three
steamboat hulks was inclosed within the dam, and that some of
the sheet-piling had not been driven through the lower one, owing
to the great resistance of the hulk and the mass above it. Boforc
the space between the lower wreck and the bed-rock could be made
secure on the inner side of the dam, the water came through and
flooded the inclosure. A stream from a powerful Gwynne pump,
having an eight-inch diameter of jet, was then directed against the
material deposited over these wrecks on the outer side of the dam,
where the water was fifteen feet deep, and enough of the deposit was
washed away to enable another course of sheet-piling to be driven
down six feet beyond the dam, through all of the wrecks, to the
rock. After this, that part of the wrecks inclosed between thisTHE EAST PIER.

5

last course of piling and the dam, was removed by a diver and the
space filled in with clay, and the inclosure again pumped out.
This portion of the dam, about fifty feet in length, was by this
construction made double. As the excavation within progressed,
it revealed the fact that another portion of the dam had been built
and made water-tight through and over a water-wheel of one of
the wrecks. The crank of an engine of seven feet stroke, at-
tached to the head of the shaft of the wheel, was just within
the inclosure, while the flanges, arms and braces of the wheel were
within the walls formed by the sheet-piling. From the in closure
within the dam were taken parts of several old and burnt steam-
boat engines, the iron parts of some of which had to be cut off at
the dam. Four wrecks of barges, some of them in use doubtless
before the era of steam, were also found within it; likewise several
oak sawlogs, some anchors, chains, and a great variety of smaller
articles lost or thrown overboard from the river craft, or dumped
in from the city.

This incongruous deposit made it exceedingly difficult to main-
tain the integrity of the dam, which at times had to resist a
pressure of thirty feet of water. Frequent floodings consequently
occurred, which delayed and increased the cost of the work.
These difficulties were, however, finally overcome, and the bed-rock
within was at last exposed to view.

On the 25th day of February, 1868, after thoroughly testing the
solidity of the rock by drilling, the first stone of your Bridge was
laid in this abutment fifty-five feet below high-water mark, about
four months after commencing the construction of the dam.

THE EAST PIER.

The caisson for sinking the east pier described in my published
report, September 1st, 1869, having been completed, and the requi-
site guide piles, air and sand pumps, hoisting machinery, ole.,
being made ready, it was launched from the ways at Carondelet
on the 18th of October, 1869, and was towed up to its position in
the river and duly secured within the guide piles on the same day.
Some days more were occupied in securing the caisson to the sus-
pension screws that were to steady it until it reached the sandy
bed of the river, and in connecting the various air and water pipes
with it. On the 25th day of October, the first stone was laid upon6

THE EAST PIER.

it, from which moment until it reached the bed-rock of the river,
on the 28th of February last (one hundred and twenty-eight feet
below high-water mark, or one hundred and twenty feet below the
City Directrix), the progress of its descent and the working of the
machinery conneetod with it, were marked by an almost total free-
dom from accident.*

During low water the normal depth of sand over the bed-rock at
this pier is about eighty feet. A rise in the river causes it to scour
down, whilst a subsidence of the flood permits the moving sands
from above to deposit rapidly and again raise the sand-bed. At
the time of placing the caisson in position the water in the river
was thirty-five feet deep, and sixty-eight feet of sand were
then overtying the rock. As the caisson descended, the current
sweeping under its bottom at the rate of about three and a
half miles per hour* caused a further scour of five feet, leaving
an irregular surface of sand, averaging about sixty-three feet
deep, above the rock. When the caisson had fairly entered
tho sand a deposit was made rapidly around it, especially in the
eddy created below the caisson. The sides of the caisson were
swept to some extent by the current, otherwise the derrick boats
on each side of it would have grounded on the deposit. This, deposit
was increased by the discharge from the sand-pumps, and by the
completion of the ice-breaker above the pier, so that for twenty or
thirty days before it reached the rock, the sand was visible above
the water, both above and below the caisson. The iron walls
of the caisson had consequently a severe external pressure upon
them from this mass of sand, and as the sides of the pier were
inclined whilst the walls of the caisson were vertical, a space was
left between the two. This space was at first occupied with bracings
against the masonry to sustain the walls. As the pier descended
and the pressure increased, sand from the pumps was discharged
into it, and in this way the walls were relieved; the height of sand
inside, between the caisson walls and the pier, being maintained at
the level of the sand on the outside. The design was to keep the
masonry constantly built up above water, as tho pier descended.
The failure of the granite company to deliver in time tho granite
which was intended to form the exterior of the pier above low-water
mark, prevented me from following out this design. At the time the

*A.n inspection of the lithographic plates in the Appendix will give the reader a clearer
idea of the method and appliances used in sinking the east and west picrB.THE EAST PIER.

7

granite was wanted, the river was from ten to twelve feet above
Jow-writer mark, and there was left only the alternative of
stopping the descent of the caisson that much above the bed-rock
and awaiting the receipt of the. granite, or else allowing the pier
to descend, and trust to the walls of the caisson to exclude the
water above the top of the pier. Three courses of granite, each
two feet thick, were^received in time, hut when the pier reached
the bed-rock the top of the masonry was about six feet below the
surface of the water.

To prevent danger to the workmen in the air-chamber, in the
event of the walls of the caisson giving way under a pressure of
water—a condition of things deemed possible, but not expected—
the shafts or wells through the masonry, by which access was
obtained to the air-locks which were at the bottom of the pier,
were kept securely built above the level of the water. On
one or two occasions leaks occurred in tho caisson walls, causing
the top of the masonry to be flooded. But this precaution
prevented a suspension of the work of filling the air-chamber
under the pier with concrete, in consequence of such accidents, as
the shafts remained free of water. During the month of April,
howeveir, the river rose to within nine feet six inches of the City
Directrix, and was nineteen feet six inches above the top of the
masonry. From the moment the caisson touched the rock up to
this time,, the filling of the air-chamber with concrete had been
progressing almost without interruption. When the water reached
this point, the walls of the caisson suddenly sprung a leak, and the
pier was again flooded in a few moments. As the flooding of the
pier usually increased the leakage in the shafts very much, it was
not found practicable to continue work in the air-chamber when it
happened, if the depth over the pier exoeeded a few feet. When
this accident occurred, the men were immediately signalled to
come up from the air-chamber, then one hundred and ten and a
half feet below the surface of the river. This they did with entire
safety. A suspension of work on the pier was then ordered until
the water should subside.

Examinations of the eaisson walls were made by our diver, Capt.
Quigley, and careful soundings were made to ascertain the depth
of the sand on the inside and outside of the caisson, ft was then
discovered that fifty-five feet in depth of the sand on the east side
of the caisson (on the outer side) had been scoured away by the8

THE EAST PIER.

action of the current, the soundings showing but thirty-five feet of
sand remaining above the bed-rock. This had reversed the strains
on the caisson walls; the corresponding fifty-five feet of sand on
the inside, between the pier and the caisson, had by its gravity
burst out the eastern wall of the caisson, now no longer supported
by the sand on the outside. This wall was of plate-iron $ of an
inch in thickness. This rupture rendered the further use of the
caisson as a coffer-dam, forever after totally impracticable. The
upper portion of it was consequently removed, and in its stead
there was secured around the pier a wooden dam, joined together
in sections corresponding to the sides and ends of the pier, and
having a large cushion near its lower edge, on the inner side, to fit
against the fourth joint of the masonry below the top course of
the pier. This work was admirably executed under the direction
of the Superintendent of Construction, Mr. W. K. McComas; the
submarine work being very skillfully performed by Capt. Quigley.
On the 13th of August the water was again pumped off from the
top of the masonry. Since this time the pier has been carried up
to the height of one hundred and seventeen feet above the bed-
rock on which it rests, and is now (October 1st) nineteen feet nine
inches above the present level of the river surface. The coffer-dam
has been removed from around it, and no apprehensions of further
trouble from water during its completion need bo entertained. It
measures at its baso, in the direction of the current, eighty-two
feet in length, and transversely sixty feet, and on the top, at its
present height, seventy-five feet seven inches by thirty-five feet
one inch. It now contains thirteen thousand two hundred and
forty cubic yards of masonry, concrete and brick work. The
vertical wells or shafts through it were lined with brick work
from thirteen to twenty-two inches in thickness. These openings
were carefully filled up with concrete, and the entire pier is now
one solid mass of masonry.

In addition to the almost constant presence of the Superintendent
of Construction, in charge of all tho works, it was made the duty
of three civil engineers, familiar with the plans, machinery, etc., to
give their personal superintendence to the sinking of the pier; one
being constantly on duty, watching the progress of the work, and
keeping a record of everything of interest occurring. The neces-
sary number of steam engineers, machinists and firemen were
employed for keeping the engines at work night and day, and theTB^E EAS^T PIER.

9

machinery in perfect order, so that the work could go on without
any interruption whatever. To accomplish this desirable object,
sufficient duplicate pumps, engines, boilers, etc., were provided, so
that the failure of any one- piece of machinery would cause no
stoppage in the progress of the work. The pier was placed on the
rock in one hundred and twenty-six days after the laying of the
first stone, which period included the most inhospitable season of
the year. The mason-work was suspended during twenty days
of this time on account of bad weather. During fifteen days it
was impossible to tow a barge of stone to the pier on account of
the running ice.

TELEGRAPH.

. When this pier had reached the depth of sixty-six feet, a tele-
graphic instrument was placed in the air-chamber, and a wire was
led to the office of the Superintendent of Construction on one of
the derrick boats at the pier, and also to the office of the Chief
Engineer in the city. By this means messages were transmitted
to and from the air-chamber, and between the offices of the Super-
intendent of Construction and that of the Chief Engineer, by which
I was, when not present, regularly advised of the progress and
condition of the work during the sinking of the pier. The
knowledge that a means of communication with the upper world
was constantly at hand in the air-chamber, and one which was not
likely to be interrupted by any accident endangering the lives of
the workmen in it, was productive of a very salutary moral effect
upon them.

These telegraphic arrangements were courteously put up com-
plete under the gratuitous superintendence of Colonel Chas. H.
Haskins, General Superintendent of the Pacific & Atlantic Telegraph
Company. The instruments were of the kind known as “ alpha-
betical,” and were easily understood and operated by those placed
in charge of them in the service of the Bridge Company.

FILLING THE AIR-CHAMBER.

The filling of the air-chamber was executed in the most careful
and substantial manner under the immediate direction of the
Superintendent of Construction. The preparation and disposition
of the concrete, were made in the air-chamber (from one hundred
and three to ono hundred and ten and a half feet beneath the10

THE EAST PIEB,

surface of the river), under the immediate supervision of Mr. Rud.
Wiesfer, C. E., Chief Inspeotor of Masonry, and his assistants,
Mr. Rich. Richardson and Mr. Fritz Eberley, master masons, one
or the. other being constantly on duty. From frequent personal
inspection, I am warranted in saying that this part of the work is
unsurpassed in excellence by that of any part of the masonry above
water.

The filling of the air-chamber with concrete commenced on the
second day of last March, and was finished on the 27th of last May,
the working time being fifty-three days* The space filled may be
fairly stated at nearly thirty-six thousand cubic feet. The area of
the base of the pier is four thousand and twenty square feet and
the height of the chamber nine feet. The caisson was stopped as
soon as it touched the bed-rock. This was at its southwest corner.
At the northwest corner its edge was eight inches from the rock.
The northeast corner was sixteen inches and the southeast corner
eight inches. It will be seen from this that the rock was fortunately
very nearly level- The sand beneath the edge of the caisson was
removed^ the rock laid bare, and the space filled carefully with con-
crete, the air. pressure being sufficient to prevent, a more rapid
infiltration of the water under the edge of the caisson than could
be managed by the pumping arrangements within it. The sand
seemed packed so firmly that no trouble was taken to barricade it
out of this space between the rock and the edge of the caisson.
When the entire edge of the caisson and the space under its two
great girders were thus concreted, the rock in its interior was
gradually cleared of sand and the concrete placed directly upon it
in layers of nine or ten inches in thickness, the closing courses
under the roof of the chamber being stoutly rammed in place. The
air-locks were then filled with the same material, and finally the
shafts. The concrete was made of broken limestone thoroughly
washed, the interstices being filled with mortar made with equal
parts of Akron cement and pure sand.

During the sinking of the pier the sand-pumps designed by me
for this special purpose gave great satisfaction and proved entire!}7
successful. One pump of three and one-half inches bore was
found quite capable of raising twenty cubic yards' of sand one
hundred and twenty feet high per hour; the water pressure required
to supply the jet being about one hundred and fifty pounds per
square inch.THE EAST PIER.

11

PRESSURE IN THE AIR-CHAMBER.

The pressure of air in the air-chamber was very accurately deter-
mined by the depth of the caisson below the surface. Any greater
pressure than that due to the depth, caused the air to escape
beneath it, but when the caisson had penetrated into the sand to a
considerable distance, it was discovered that the water level formed
by the air under or across the bottom of the chamber was nearly
a foot lower than the bottom edge of the caisson. When the
caisson was but a few feet in the sand, the air forced its way up
by its sides in one or two currents of large volume; but as it
penetrated more deeply, the passage of the air through the sand
evidently became more difficult, and it appeared in small
bubbles sixty or seventy feet distant from the caisson. This
retardation of the escapement of the air from beneath the caisson
caused an increase of air pressure, by which the water was held at
a greater or lesser depth below the line of the bottom of the air-
chamber. The sand inclosed in the air-chamber and forming its
floor was usually one or two feet more elevated than the lower
edge of the chamber, and was entirely devoid of water, the air
pressure expelling the water from it down below the edge of the
caisson, as just stated. The distance to which it was thus expelled
and maintained was at no time discovered to exceed ten inches,
and generally it was not over eight inches. This would give an
air pressure equal to nearly one foot more than the depth of the
caisson, or about one-third of a pound per square inch more. This
difficulty of escapement of the air through the sand was in-
creased somewhat by concreting under the edge of the caisson
on the rock, and the actual air pressure could then bo no longer
accurately determined by the height of the water above. The
pressure gauges usually indicated a pressure of one or two pounds
more than the depth of the water would give by calculation. This
was caused in a great measure, however, by the friction of the air
in the pipes, the gauges being at the pumps and not in the air-
chamber. A column of water one hundred and ten feet six inches
in height would be equal to a pressure of 47.96 pounds per square
inch, assuming the weight of the water to be 62.6 pounds per cubic
foot*. The greatest pressure marked by the gauges was fifty-two
pounds, and it is not probable that the pressure in the air-chamber
over exceeded fifty or fifty-one pounds.12

THE EAST PIER.

EFFECTS OF COMPRESSED AIR ON THE MEN.

The first symptom manifesting itself, caused by the pressure
of the air, is painfulness in one or both ears. The Eustachian tubes
extending from the back of the mouth to the bony cavities over
which the drums of the ears are distended, are so minute as not to
allow the compressed air to pass rapidly through them to these cavi-
ties ; and when the pressure is increased rapidly, the external pres-
sure on the drums causes pain. These tubes constitute a provision
of nature to relieve the ears of such barometric changes as occur
in the atmosphere in which we livo. The act of swallowing facili-
tates the passage of the air through them and thus equalizes the
pressure on both sides of the drums, and prevents the pain.
The pressure may be admitted into the air-lock so rapidly that this
natural remedy will not in all cases relieve it. By closing
the nostrils between the thumb and fingers, shutting the lips
tightly and inflating the cheeks, the Eustachian tubes aro opened,
and the pressure on the inner and outer surfaces of the tympanum
is equalized and the pain prevented. This method must be
used and repeated from time to time as the pressure is let on,
if it be increased rapidly. No inconvenience is felt by the reaction
when the pressure is let off, as the compressed air within the
drums has a tendency to open the tubes, and thus facilitates its
escape through them ; whereas increasing tho pressuro has the effect
of collapsing them, and therefore makes it more difficult to admit
the compressed air within the cavities of the ears. It frequently
occurs, however, from some abnormal condition of these tubes, as
when inflamed by a cold in the head, that neither of these remedies
will relievo the pain. To continue the admission of compressed
air into the lock, under such circumstances, would intensify
the suffering, and possibly rupture the tympanum, therefore
the lock tenders were particularly instructed to shut off
the compressed air at the moment any one in tho lock
experienced pain about the ears; and then, if it could not
be relieved by the above means, the lock was opened and the
person was not permitted to go through into the air-chamber.
Sometimes fifteen minutes were occupied in passing persons
through the first time, after which they usually had no further
trouble from this cause.

The fact that the depth penetrated by the air-chamber was con-THE EAST PIER.

13

siderably greater than that hitherto reached in any similar work,
left me without any benefit from the experience of others, in
either guarding against any injurious effects of this great pres-
sure upon the workmen and engineers subjected to it, or of
availing myself of any known specific for relieving those affected
by it. When the* depth of sixty feet had been attained, some
few of the workmen were affected by a muscular paralysis of
the lower limbs. This was rarely accompanied with pain, and
usually passed off in the course of a day or two. As the
penetration of the pier progressed, the paralysis became more
difficult to subdue. In some cases the arms were involved, and
in a few cases the sphincter muscles and bowels. The patients
also suffered much pain in the joints when the symptoms were
sovere. An average of at least nine out of ten of those affected
suffered no pain whatever, but soon recovered, and generally
returned to the work.

The duration of the watches in the air-chamber was gradually
shortened from four hours to three, and then to two, and finally
to one hour.

The use of galvanic bands or armor seemed, in the opinion of
the Superintendent of Construction, the foreman of the chamber,
and the men, to give remarkable immunity from these attacks.
They were all ultimately provided with them. These bands were
made of alternate scales of zinc and silver, and were worn around
the wrists, arms, ankles, and waist, and also under the soles
of the feet. Sufficient moisture and acidity were supplied by
the perspiration to establish galvanic action in the armor, and
as the opinion among those most accustomed to the chamber
was almost unanimous in favor of this remedy, I am very much
inclined to believe it valuable.

Immediately on the manifestation of greater severity in the
symptoms, a hospital boat was fitted up at the pier, and one of
the ablest physicians in the city (Dr. A. Jaminet) was engaged to
attend those affected, and also to institute such sanitary measures
as his judgment should dictate. A careful examination of the
health and bodily condition of every workman was daily made, and
none were permitted to engage in the work without the approval
of Dr. Jaminet. Those most severely affected were sent to the
City Hospital, and had the benefit of the advice and treatment of its14

THE EAST PIER.

rosident physician, Prof. E. A. Clark. The total number of men
employed in the air-chamber of this pier was three hundred
and fifty-two. Of this number about thirty were seriously
affected. Notwithstanding the care and skill with whioh those
most severely attacked were treated, twelve of the cases proved
fatal. Each one of these, without exception I believe, was
made the subject of careful inquest by the coroner, aided by an
autopsy, conducted usually by some of our most skillful surgeons
and physicians. Whilst the exciting cause in all of these cases
was doubtless the exposure of the system to the pressure of the
condensed air of the chamber, the habits and condition of several
of those who died were, at the time they went to work, such as
would have oxcluded them from it if subjected to the examination
of Dr. Jaminet, and the verdict in about one-half of the cases
gave a totally different cause for the death of the patient.
Nearly or quite all of these deaths happened to men unaccustomed
to the work; several of them to men who had worked but one
watch of two hours. In contrast to this is the fact that quite a
largo number of the men (certainly one-half of those constantly
employed) commenced with the work at its inception and
remained throughout its continuance entirely without injury or
inconvenience.

The gentlemen composing the engineer corps of the bridge all
visited the air-chamber, some of them quite often, either in the
discharge of their professional duties or from motives of curiosity,
and none of them suffered any injury whatever.

Much diversity of opinion was expressed by the medical gentlemen
who investigated the symptoms and held autopsies of the deceased.
Some of these gentlemen maintained that a slower transition from
the abnormal to the natural pressure would havebeen less injurious;
others claimed, on the contrary, that it was from the too rapid
application of pressure in passing from the natural into the com-
pressed air. The fact that the air-lock tenders were in no case
affected, although subjected many times during a watch of two
hours in the air-lock to rapidly alternating conditions of the
atmosphere, at one moment in its normal state in the lock, and
five minutes later exerting a pressure of fifty pounds per square inch
upon every part of the body, would seem to prove both of these
theories unsound, and lead us to believe that in the length ofTHE EAST PIER.

15

time to which the human system is subjected to this extraordinary
pressure, exists the real source of danger, and not from any rapid
alternations of pressure to which it is exposed. After the caisson
reached the rock, I have frequently, when passing through the
air-lock, admitted the compressed air into it so quickly that none
but those well accustomed to it could relieve the pressure upon
their ears, and yet I felt no ill effects whatever from this rapidly
increased pressure; and in going out T have let the pressure off
so fast that the temperature in the lock had fallen thirty-two
degroes (Fahrenheit)* in consequence. These transitions occupied
but three or four minutes.

The fact that the air-chamber was briefly visited by thousands
of persons, ineluding many delicate ladies, even after it had reached
the bed-rock, some remaining as long as an hour in it without any
of them experiencing the slightest ill effects from the pressure,
and the fact that no cases of any importance whatever occurred
among the workmen after the watches were reduced to one hour,
satisfies me that this is the true cause of the paralysis, and that
by lessening still more the duration of the watches, a depth con-
siderably greater can be reached without injury to the workmen.
Too long a continuance in the air-chamber was almost invariably
followed by symptoms of exhaustion and paralysis. Dr. Jaminet,
on one occasion, remained in two and three-quarter hours when
the depth was over ninety feet, and was dangerously attacked
soon after reaching home.

Symptoms of paralysis rarely occurred in tne shaft, but gen-
erally after the stairs were ascended, and never in the air-lock or
air-chamber.

A large amount of money has been gratuitously expended
by the company in assisting and providing for those who were
seriously affected, and in relieving the wants of their families
during their illness.

As a merited recognition of the eourage, fidelity add services
of the men employed in the air-chamber of the east pier, and as
an evidence of my personal appreciation of their faithfulness and
good conduct, I have placed in the appendix to this report, the
names of those engaged in the work when the pier reached the
rock.16

THE WEST PIER.

THE WEST PIER.

The sinking of the west pier began on the fifteenth day of
January of last year, that being the day on which the first stone
was laid on the caisson. As it was commenced twelve weeks later
than the east pier, advantage could be taken of the experience
gained in sinking the latter. On the east pier the interruption
and annoyance caused by the necessity of riveting on the iron
plates outside of the masonry to exclude the water, as the pier
descended, led me to devise some means whereby this inconve-
nience might be prevented and the cost of the iron saved. The
design of the west caisson was so modified that the use of these
plates could be abandoned after the first twenty-nine feet; nine
feet of this height being the air-chamber, and the remaining twenty
feet enveloping the masonry above the chamber. This height
of plate-iron was deemed requisite to give such rigidity to the
caisson as would insure it against any twisting or straining that
would endanger the bond of the masonry. After a depth of forty
or fifty feet was reached by the east pier, it was found evident
that brick linings in the shafts, although surrounded by many
feet of masonry carefully laid in hydraulic cement, were not suffi-
cient to exclude the water, which at this depth filtered through
quite rapidly. To prevent this and enable tho iron around the
outside of the pier to be dispensed with on the west pier, its shafts
were lined with white pine staves, three inches thick in the centre
shaft, which was ten feet in diameter, and two and a half inches
thick in the smaller wells, which were four feet nine inches in
diameter. This device answered admirably, and the estimated
saving in plate-iron over the original design was about 810,000.
The lower staves were, however, found to be too weak to sustain
the high water of the spring freshet without expansion bands of
1x3 inch bar-iron, which were placed against them in the shafts in
time to avoid any disaster. This novel feature of wooden linings
and no exterior envelope for the masonry, will be introduced in the
east abutment. The caisson for it is, however, made so strongly,
that the iron will only be brought up to a height of twelve feet
around the base of the masonry. The lining staves in its wells
will be so much stronger that they will require no internal sup-
porting rings of iron.

Nothing could have exceeded the perfect working of these
economic improvements in sinking the west pier, had not thoTHE WEST PIER.

17

contractors failed to deliver the granite for it in time. When the
point was reached at which the granite bccamo necessary, the
surface of the masonry was six or eight feet above water and the
base of the pier eightoen or twenty feet from the rock. A
judicious view of the case, having reference solely to the cost of
constructing this pier, would have dictated a suspension of the
work until the stone should have arrived, rather than continuo
the sinking of the pier and suffer the top of the masonry to
descend below the surface of tho water. Other questions, howevor,
were involved of a -more serious nature. It was universally
conceded that any effort to negotiate the securities of the Company
would be fruitless unless preceded by an absolute demonstration
of the practicability of putting down the channel piers of your
Bridge upon the bed-rock of the Mississippi, through the unusual
depths of water and sand that were to be encountered. The east
pier was in a similar condition at this time, and there remained no
alternative but to continue sinking both, to do which it was
necessary to build up and brace out the iron plates which bad been
carried Up from tho air-chamber around the masonry of the last
pier, and thus dam out the water from covering the top of the
masonry as it descended below the surface of the Mississippi, so as
to be able to resume the laying of stone when tho gi’anite should
arrive; and as the west pier was without any such iron envelope,
it became necessary to attach the wooden walls of a coffer-dam to
its sides in sqch a manner as to exclude the water from the top of
the pier. This was done by padding the lower edge of tho dam and
attaching its sides securely to the masonry, several courses below
the top. This answered very well until tho last nine inches of this
pior was sunk to the rock. Some of the bolts holding down tho
dam at the south end of the pier gave way, and tho friction of the
sand, then fourteen feet high on the outside of the dam, and nearly
to the surface of tho water, prevented tho settlement of the dam
with the pier at this particular point. Two outside courses of
the limestone to which it was attached were held up by the dam
nearly across the entire end of tho pier. This mishap made it
necessary to pump away the sand outside this end of the dam, and
put down a large pad or wooden covering reaching below the two
disturbed courses, then pump out the dam and relay them. This
was done at a depth of about seventeen feet below tho surface.
The dam was not pumped out till the granite arrived, as the water
over the pier did not prevent tho work in the chamber, access to
218

the east abutment pier.

it being obtained through the wooden shafts or wells which passed
down through the water that was over the masonry. This unex-
pected trouble, and that at the east pier, were caused solely by the
failure of the Richmond Granite Company to deliver the granite in
time. Its delivery was due several months before it was needed,
and yet it was not delivered until several months after it was
wanted. The loss to your Company, resulting from this failure, I
estimate to amount to at least $50,000.

tiie east abutment tier.

The complete success which attended the sinking of the east pier
convinced me of the practicability of sinking- the east abutment
pier to the rock in the same manner. The original plans of the
Bridge did not contemplate resting this abutment on the rock. It
was believed quite practicable to protect its foundation with'riprap
stone, and to secure stability and safety by resting it on piles,
which were to have been driven to a distance of fifty feet below
low-water mark. When the Directory of the Company were assured
of the practicability of resting this abutment upon the bed-rock
itself, and of thus terminating forever all doubts as to the absolute
stability of each one of the four great piers of your Bridge, the
desire that this, the largest of them all, should be placed on the rock
also, was unanimous; although the excess in cost involved over
that of the original design was understood to be about $175,000.
No less than ten thousand additional cubic yards of masonry below
the line of the tops of the piling on which it was originally
intended to start the masonry, are required to sink the pier to the
rock. Consequently, below this line it will require nearly as much
masonry as will bo contained in the west abutment when the latter
is completed.

This abutment, when completed, will contain twenty-two thou-
sand four hundred and fifty-three cubic yards of masonry, including
ooncrete and brick-work, and will measure in height, from the rock
to the top of its cornice, one hundred and ninety-six feet nine
inches.

The depth of the rock at the site of the abutment was ascer-
tained by careful borings to bo eight feet lower than that at the
east pier, or one hundred and thirty-six feet below high-water
mark.THE EAST ABUTMENT PIER.

19

It is not probable that wo shall have to contend with much deeper
water or much greater air pressure than that encountered in sink-
ing the east pier. The bed-rock at this abutment is ninety-four
feet below extreme low-water mark, and the river is not likely to
be more than eighteen feet above that during the seasons occupied
in sinking the pier. Extreme low-water mark is only reached
when the river is gorged with ice above the city, and the volume of
water below the gorge becomes in consequence greatly lessened.
The ordinary low water rarely reaches a point within five feet of
low-water mark.

In accordance with the wish of the Directory, preparations for
sinking this abutment to the rock were commenced, and are now
nearly completed. The caisson is nearly ready for launching,
after which it will be immediately towed into position, and be
made ready for sinking. It will cover, when on the rock, five
thousand square feet of surface, and is therefore about one-quarter
larger than the base of the east pier. A large trestle-work has
been erected immediately oast of the site of this abutment, extend-
ing a fow feet above high-water mark, on which is being placed a
portion of tho necessary machinery for sinking the caisson. This
trestle-work was rendered necessaiy because of tho shallowness of
tho water on that side of the abutment. On the west side of the
caisson one of the derrick boats used at the east pier will be
located, and on the trestle-work will be placed much of the
machinery of the other derrick boat, which was used on the other
side of the east pier.

THE EAST ABUTMENT CAI8SON.

This caisson will have sevoral novel features in its construction,
which I think will make it superior to those used for the east and
west piers. The main shaft will have at the bottom two air-
locks, each eight feet in diameter, instead of one of but six feet.
The main shaft will be carried down into the air-chamber ten feet
in diameter, instead of but five feet.

Tho east pier caisson had six other shafts of four feet nine inches
in diameter, with air-locks of the same diameter at the bottom of
each. This caisson will have but two other shafts of four feet in
diameter, with an air-lock at the bottom of each, eight feet in
diameter. These last two shafts are enlarged below the roof of tho
air-chamber to eight feet in diamoter each. The increased di-20

THE BAST ABUTMENT PIER.

ametcr of the looks will contribute to the health of the men, as it
is sometimes necessary for twelve or fourteen of them to be in ono
of them at the same time, for several minutes, until the pressures
are equalized. As all four of these locks are within the air.
chamber, and also the lower ends of the three shafts, and as about
one thousand eight hundred cubic feet of space is occupied by
them, there will be that much less space to fill in the compressed
air when the pier is down.

The centre shaft alone will be used for the workmen, unless
some unforeseen accident should render it necessary for them to
use one or the other of the side shafts, which are provided almost
solely for safety. The extra size of the locks makes oither one of
them capable of holding, in an emergency, all the men that will be
in the air-chamber at ono time, and hence their security will be
increased.

To avoid the labor of walking up a circular stairway about one
hundred and twenty feet high after leaving the air-chamber, the
main shaft, in addition to the stairway, will have an elevator or lift
to bring the men up. This, it is .believed, will contribute greatl}'
to their health. When they are at work in a pressure of forty-
five or fifty pounds above that of the natural atmosphere, there
ensues a rapid exhaustion of the physical energies. When
relieved from duty, a considerable degree of prostration is fre-
quently manifested, and the foremen of the different gangs were in
consequence instructed by the physician to cause the men to
ascend the stairs leisurely, to avoid increasing it. I confidently
believe, therefore, that by bringing the men to the surface in the
elevator, there will be much less danger of injury occurring from
their employment in the air-chamber.

LIGHTING THE CAISSON.

A different method of lighting the air-chamber will likewise be
adopted. In the other caissons much inconvenience was experi-
enced on account of the particles of (unburned carbon thrown off
from the flames of the candles used. The consumption of the candles
under the action of the compressed air was much more rapid than in
the normal atmosphere. At the depth of one hundred feet, they
were found to bo consumed in about three-fifths of the time re-
quired in the open air. Large quantities of smoke were emitted
from the flames, and the air was filled with particles of floatingTHE EAST ABUTMENT PIER.

21

carbon, which could only be removed thoroughly by placing a rose
jet on the nozzle of a water hose in the chamber, and discharging
the spray in every direction. Some amelioration of the evil was
obtained by burning the candles under an inverted funnel or
chimney, communicating with one of the shafts by a small outlet
pipe, through which the escape of the compressed air was regulated
by a cock, thus creating a draft above the flame by which the
smoke was carried off.

The calcium light would probably prove the most satisfactory
one which could be employed in the chamber, were it not for the
excessive cost of it in this city. For the one hundred and fifty
days which will be required in sinking this pier and completing its
foundation on the rock, the cost of lighting the three compart-
ments of the chamber with calcium lights would be at least $5,000.
By the means devised for the purpose the cost cannot 'exceed
one-fifth of that sum.

The difficulty of extinguishing a flame in an atmosphere of such
densit}’, caused mo to forbid the use of oil lamps in the chamber
before a depth of eighty feet had been reached. The clothing of
two of the men having taken fire from contact with some of the
hand-lamps or candles used in tho caisson, it was found exceedingly
difficult to extinguish the flames. One of them was severely
burned, although his garments were almost entirely woolen. It
was deemed unsafe to risk tho danger of having the clothing of the
men saturated with oil from the accidental breaking of a lamp,
which might, by tho same casualty, ignite their garments and thus
endanger their lives. Tho use of oil was therefore forbidden.

At the depth of eighty feet it was found that the flame of a
candlo would immediately roturn to tho wick after being blown out
with the breath. At the depth of one hundred and eight and
one-half feet below the surface of the river, I blew out the flame
of one of them thirteen consecutive times in the course of half a
minute, and each time, excepting the last, it returned to its wick.
Almost as long as a small portion of the wick remained incan-
descent, the flame would return, and when the glowing particle of
two separate candles failed to possess sufficient heat to restore the
flame to either, it would reappear at once by placing the luminous
portions of the two wicks in contact.22

THE BAST ABUTMENT PIER.

The chamber of this caisson will be lighted by candles contained
within glass globes of similar construction to those used in lighting
railway carriages. The glass will be of strength sufficient to
sustain the external pressure of the condensed air. The chimney
will consist of an outlet pipe of one inch diameter, communicating
with one of the shafts, and the compressed air will only be
admitted within the globe in which the candle is placed, through a
small regulating valve. The candle will therefore be burning
under the normal pressuro of air. A stop-cock in the chimney
will prevent the escape of air from the chamber through the
globe, when it is desirable to put in another candle, or to clean
the glass.

TIMBER WORK.

Beneath the masonry piers of suspension and truss bridges, it
is quite common to employ a considerable amount of timber.
Where the pressure upon the pier is a vertical one, this economical
substitute for stone is admissible, but in the piers of an arched
bridge, where some one span is at times loaded while the others
are unloaded, the thrust of the loaded arch has a tendency to
oscillate the piers; and with a few feet in thickness of a material
so elastic as wood under their bases, this oscillation would prove a
dangerous feature. In the abutment piers, where the thrust is
only from one side, and oscillation is prevented by the works on
shore, timber may bo safely used to a considerable extent. To
give tho desired stiffness to the caisson for this abutment and
avoid the more costly use of iron, the roof of the air-chamber is
made of timber four feet and ten inches in thickness. A large
amount of timber is also used in constructing and stiffening the
sides of the air-chamber, which are ten feet high, and in forming
two horizontal trusses or girders through the air-chamber. Those
two girders are each ten feet thick at the top, three and one-half
feet at the base, and nine feet in height. They are about seventy-
three feet long, and are interlocked at each end with the sides of
the air-chamber. They divide this chamber into three nearly equal
compartments in the direction of the length of the Bridge. Com-
munication is made between these compartments by means of two
openings through each girder.

The sides of the chamber are eight and one-half feet thick
at the top and eighteen inches at the bottom, and arcTIIE EAST ABUTMENT PIER.

23

composod of timbers, some placed vertically, others horizontally,
and some inclined at an angle of about forty-five degrees, and the
whole, including roof and girders, thoroughly interlocked together,
and bolted with large iron bolts. All of the timber is of the very
best white oak, and was squared up with two steam planers be-
longing to the Company. In addition to the iron bolting used,
these timbers are thoroughly secured together with large white
oak tree-nails.

The wood-work of the caisson has been most admirably executed
under the superintendence of Mr. John Dunlap, master of ship-
carpenters.

PLATE-IRON WORK.

Enveloping this entire wooden structure is an iron covering
riveted together to prevent the escape ot the air which is to supply
the workmen. This is of three-eighth inch plate-iron, and its sides
are increased in thickness at the bottom edge to three inches, by
riveting four three-quarter inch plates together. These extend
several feet up the sides. This iron edge extends ten inches down
below the wooden sides and forms the cutting cdgo of the caisson.
Every two feet the iron sides are strengthened by vertical angle
irons three by seven inches in size, riveted on flat-wise on the
outside of tho caisson. Through these angle bars, bolts one and
a half inches in diameter are inserted, and by them the iron and
wooden sides are strongly held together. This iron covering
extends over the wooden top of the air-chamber and forms a floor
on which the masonry will be laid. The three shafts passing
through this floor, by which access to tho chamber is obtained, are
tightly riveted to it.

The iron sides are carried up twelve feet above this floor, where
they will terminate. The masonry above this point will therefore
have no exterior envelope such as the east pier had.

Nearly all of the iron used in this envelopo was obtained from
the hull of the iron gunboat Milwaukee, the wreck of which was
purchased about eighteen months ago. This iron-work has been
executed by Capt. Wm. S. Nelson, the skillful and energetic con-
tractor who built tho caissons of the two channel piers.24

THE EAST ABUTMENT PIER.

WATER-TIGHT LININGS.

The water penetrating the masonry will be excluded from the
three shafts by white pine linings, arranged like the staves of a cask.
The staves composing this lining in the main well or shaft, which
is ton feet in diameter, will be ten inches thick in tho lower part,
and will be gradually diminished to three inches at the top. In
sinking the pier, the top of the masonry and shafts will be kopt
constantly built up above the surface of the river.

FILLING THE AIR-CHAMBER.

The most valuable improvement in tho design of the caisson*
will, I think, bo found in tho method devised for filling the chamber
when it has reached the rock. It is a woll-established fact that
sand constitutes one of tho most reliable and durable materials for
foundations known, if availed of in positions whero it can be se-
curely retained under the structure erected upon it. It is an equally
well-established fact that timber, when entirely submerged in fresh-
water foundations, is indestructible. These two facts will be relied
upon in filling the air-chamber and fixing the foundation of this pier
upon the rock. Instead of concrete, sand will be chiefly used for
filling the chamber. Tho sides of the caisson are of great thick-
ness, and are thoroughly interlocked at the corners of the air-cham-
ber and at the ends of the girders. The possibility of the sand
surrounding tho pier ever being scoured out to the rock at the site
of this abutment, is a very remote one. It is certainly much more
improbable than that it may bo scoured thus deeply at the sites of
the two channel piers. To avoid all danger from this very remoto
possibility throughout all time, whatever space there may be exist-
ing between the timber walls of the caisson and the bed-rock, after
the caisson shall havo reached it, will be thoroughly concreted, so
that these walls will have a substantial bearing upon a solid mate-
rial which cannot bo affected by any current that may possibly
wash the base of the pier. The walls of tho air-chamber are so
framed as to bo sufficiently strong to resist the bursting pressure
of the sand within the chamber, caused by the weight of the ma-
sonry of the pier and half the side span upon it, even after all the
iron used in it shall have been corroded away. The base of the
pier is 5,000 square foet in area, and the weight of the ontire pier,
including one-half of the span, will bo about 46,500 tons. TheTHK EAST ABUTMENT PIER.

25

pressure per square foot on the rock would, therefore, be 18,600
pounds. The area of the wooden edge of the caisson, including
that of the bottom of the girders, air-locks and shafts, is about
1,250 square feet. This area alone would be capable of sustaining
the pier, without any additional support from the sand contained
within the air-chamber. Without this sand-filling, the pressure
upon the wooden base of the caisson (including the locks and
shafts) would be about 74,000 pounds per square foot, or 514 pounds
per squaro inch. This pressure is not beyond the power of good
white oak to resist, nor would it be sufficient to crush the concrete
that will be used in filling the small space between the oak and
the rock.

Tests made with our testing machine upon a number of blocks
of concrete only six weeks old, gave an average resistance to
crushing, equal to one thousand two hundred pounds per squaro
inch. Of courso, with the integrity of the exterior of the caisson
unimpaired, the escape of sand from the interior would be impos-
sible. With the interior compactly filled, the pressure of the
superincumbent mass must necessarily be very nearly equally
distributed over every part of the caisson, and hence it cannot
oxceed about 18,600 pounds per square foot.r

The tedious process used in concreting the air-chamber of the
channel piers, together with the objections to working men at such
great depths, induced me to devise some method by which a
smaller amount of manual labor could be made to accomplish
oqually good results. By the plan determined on in this case, I
confidently hope to accomplish the necessary work in the air-
chamber with a fifth or sixth of the manual labor which was
required under the east pier.

This method is so simple as to be readily explained. So soon as
the rock shall have been struck by the iron edge of the caisson,
the space then remaining betweon the wooden walls of the caisson
and the rock will be thoroughly concreted. The sand under,
the two girders will be left intact. The borings indicate that
the rock is quite level, and it is not probable that inequalities
of more than eighteen inches will be found in it. It is estimated
that one hundred cubic yards of concrete will be sufficient
to support these walls, forming a bed of an average width of
three feet six inches, by two feet six inches in height. This
concreting being done, all of the pipes passing vertically26

THE WEST APPROACH.

through various parts of the pier, and used for air, Water, and
sand pumps, will be closed at the top, and the pumps, valves and
pipes connected with them in the air-chamber will then be taken
off. There will be nineteen of these vertical pipes, each either
four or six inches in diameter, the lower ends of which will be
enlarged conically through five feet of their lengths. Those pipes
being opened at their lower extremities, and one of the inner
doors of an air-lock being secured from being clogged by sand*
the air from the chamber will be permitted to escape, and the
chamber will be filled with water. This being done, sand will be
introduced through the various vertical pipes mentioned. By
means of plummets in these pipes, we shall be able to determine
the height of the sand discharged in them, and when it is near the
roof of the chamber the air will bo again pumped in, and workmen
will be sent to level it off. By repeating this process two or three
times, the chamber can be filled nearly to the roof with sand
compacted in waler, which will insure its solidity. The remaining
space can then be filled with concreto rammed in under the roof of
the chamber. The great thickness of the walls and of the girders
whore they join the roof reduces the area of the upper part of the
chamber very greatly. The upper three feet of it measures only
two thousand and twenty-five cubic feet in area, exclusive of the
air-locks and shafts.

i'

To fill the air-chamber of the east pier required one thousand
throe hundred and forty cubic yards of concrete, which was placed
in position by manual labor, under an air pressure of nearly fifty
pounds per squaro inch. This pier is twenty-five per cent, larger,
and will require only about two hundred cubic yards of concrete
to be placed in it under similar conditions; honce the work
required to be done in this chamber will bo greatly less than in
that of the east pier.

WEST APPROACH.

In this approach, which will be entirely of stone, there will bo
five arches of twonty-six feet eleven inches span, and forty-two
feet ten inches in height above the level of the street. The found-
ations for the piers to support these arches all rest upon tho
rock underlying the wharf. These foundations are nine feet
by forty-six foot six inches. Tho one next to the west abut-TIIE EAST APPROACH.

27

ment is the deepest of the five, the rock being forty-one feet oight
inches below the City Directrix. This foundation is already com-
pleted and will soon receive the Missouri rock-faced red granite,
which will form the base for the fine cut sand-stone, of which the
approaches, on each side of the river, will be built. The founda-
tion for the second pier of this approach has just been commenced.
The foundation for the third and fourth piers are completed and
are ready for the sand-stone. The masonry already laid in theso
three approach piers measures nine hundred cubic j'ards.

The foundation for the fifth pier will bo in the line of the houses
fronting the wharf, and has not yet boon commenced. The cellars
of the houses, where it is to stand, have been blastod out of the
solid rock, and this pier will be rapidly and easily constructed
when commenced.

THE EAST APPROACH.

The piers for this approach will bo built upon pile foundations,
none of which have yet been commenced.

There will bo no difficulty in completing this approach within
the desired time, and it will be more convenient and economical to
begin it after the work on the west approach is more advanced.
In design it is almost exactly like the west one.

SAND-STONE.

In the selection of sand-stone, tho greatest possible care has
been exercised. This selection was more especially supervised
by Colonel W. Milnor Roberts, Associate Chief Engineer, who
personally visited and carefully inspected every sand-stone quarry
of any note within available distance of the work. The one
selected lies close to the Mississippi river, near Ste. Genevieve, and
is distant about sixty-five miles from St. Louis. The stone is a
pure sand-stone, of a warm yellowish tint. It is of uniform color,
free from blemishes, and from the tests made of it, promises great
durability.

A force has been at work for some time getting out and cutting
the stone, and no fear of delay is entertained on account of non-
delivery of it in time.28

GRANITE.

GRANITE.

Colonel Roberts has also devoted much of his time to the
selection of the granite used, and to be used, in the construction
of 3Tour Bridge. Several examinations were made by him of
the Eastern granites, and almost every quarry from Richmond
to Buck’s Harbor, in Maine, was visited by him, with a view to
obtain tho best and cheapest that could be had. A contract for
the first seven hundred cubic yards was made by him with the
Richmond Granite Company for gray granite. Subsequently,
another was made with Messrs. Thomas Westcot & Son, of Maine,
for all the gray granite that will be required for tho two abut-
ments and tho two channel piers. All four of these piers will
bo faced with granite ashlar above extreme low-water mark,
except those parts of their sides which are above the springing
of the arches and beneath the roadway, and inclosed between
the spandrels of the arches. This portion, which is much less
exposed to the weather and to view, will be of cut sand-stone.

Missouri red granite will also be used as ashlar, but only
in tho bases of the approaches, and on the T walls of tho
abutments, and will appear only to the height of the curb-stone
on the St. Louis wharf, which is nearly the level of the City
Directrix. For this purpose about fourteen hundred cubic yards
will be required. This granite promises to be equally as durable as
the gray, and that which is already laid up in the work is greatly
admired on account of the richness and beauty of its color.

It is to bo regretted that proof could not have been given, at
an earlier date, of the capacity of a Missouri quarry to supply
a material so excellent and desirable. One of tho good results
of your enterprise is the discovery and development of this ex-
tensive quarry, owned by Hon. B. Gratz Brown, with whom a
contract was made last April for 1,400 cubic yards of the stone, a
great part of which has been already delivered. This quarry is
distant ninety miles from St. Louis and three miles from the-Iron
Mountain Railroad.

Several hundred dollars were expended by the Bridge Company
in fruitless endeavors to obtain tho proper quality of gray granite
from a quarry in this State, prior to this contract, and this dis-TESTS OF GRANITE.

29

couragement, together with the unfavorable results of examina-
tions made of other unproved quarries in this State, created a
reasonable assurance that no suitable granite would bo discovered
in Missouri, in time for our wants. Hence, no alternative re-
mained but to seek for it elsewhere.

TESTS OF GRANITE.

In the Appendix will be found two interesting reports, one from
Prof. Felix McArdle, and the other from Dr. Enno Sander, chem-
ists of high standing in St. Louis, giving the chemical tests applied
by them, and the results produced by these tests upop the samples
of red granite now being used in tho construction of your Bridge.

The very careful experiments and report of Prof. McArdlo were
made gratuitously.

A resolution thanking him for this generous manifestation of
his interest in your enterprise, was passed by the Board of Direct-
ors ot tho Bridge Company.

MAGNESIAN LIMESTONE.

The interior of all the masonry will bo of magnesian lime-
stone from the Grafton quarries. None of this stone will be
exposed to the weather. It is remarkably strong. Many tests
of its compressive strength have been made in the Company’s
tosting machine, where its resistance has, in several instances,
exceeded 17,000 pounds per square inch, which is equal to that of
granite.

A curious fact has been developed by theso tests, which is that
the modulus of elasticity of this stone is about the same as that of
wrought iron. That is, a given weight placed upon a wrought
iron column and on a column of the Grafton stone of the same
size, will produce an equal shortening in both; while the elastic
limit (or breaking point) of the stone is not far below the limit at
which wrought iron would bo permanently shortened. A column
of tho stone two inches in diameter and eight inches long was
shortened undor compression in tho testing machine nearly one-
quarter of an inch without fracturing it. When the strain was
removod the piece recovered its original length.BO

TESTING MACHINE.

TESTING MACHINE.

The testing machine, the design of which was made by Colonel
Henry Flad, Chief Assistant Engineer, has been in operation for
several months, and has given the greatest satisfaction. B}t means
of a very simple little instrument, suggested by Chancellor Chau-
vcnet, and matured by Col. Flad, the most delicate changes in the
length of the specimen can be accurately recorded, with a degroe
cf minuteness never before obtained or even approximated in any
testing machine, so far as my information extends. By this instru-
ment it is perfectly easy to detect a change in the length of the
piece equal to the two hundred thousandth part of an inch.

A brass collar is slipped over each end of the specimen, and these
are secured by threo pointed set screws in each collar. Any short-
ening or lengthening of the piece will, of course, alter tho distance
between the two collars. One collar has on the side of it a small
flat surface or vertical table. Against this table is placed a little
vertical steel cylinder, which is held against the table by the end
of a little flat horizontal bar that is secured at its other end to the
other collar. This bar is held against tho steel cylinder by a spring,
having sufficient strength to keep the cylinder from falling. It is
evident now that if one collar be brought nearer, or is moved
further away from the other, the steel cylinder will be rotated, as
one side of the cylinder is pressed against the table, which is attached
to one collar, while the other side is pressed by the little bar that is
fastened to tho other collar. If tho specimen be subjected to pres-
sure it will be shortened and the collars will approach each other.
If tension be applied to tho specimen, the piece will bo stretched
according to its intensity, and in either case tho rotation of the
little steel cylinder will indicate the measure of the disturbance that
has occurred between the two collars, and it will give it absolutely
without any element of error ontering into it from any change of
the dimensions of parts of the machine under strain. By placing
on tho top of this little cylinder a small vertical mirror, the extent
to which the cylinder has been rotated may bo determined in
the following manner:	Twenty-five feet from tho mirror, an arc of

a circle is struck, the little steel cylinder being the centre of the arc.
On this arc is erected a scale of inches with decimal subdivisions.
This scale being illuminated by gas-light can bo easily road in tho
mirror by means of a small telescope placed immediately above thoTESTING MACHINE.

31

scale. The angles of incidence and reflection at the surface of the
mirror being equal, it follows that one-fourth of a complete rotation
of the mirror would be equal to a half circuit of the circle of which
the arc is a part; or, in other words, a movement of the mirror of
but one degree would be shown on the scale by the reading of a
space equal to two degrees, or the one-hundredth part of an inch on
the scale would really be only half so much, or the two-hundredth
part of an inch, when scon in the mirror. Tho diameter of the
little cylinder is so proportioned to the radius of the arc as to
make tho smallest subdivision of the scale equal to the twentj*-
thousandth part of an inch, but tho observer, after a little practico,
can subdivide these divisions, which are magnified by the telescope,
so as to observe the two hundred-thousandth part of an inch.

The power is applied to tho specimen under trial by means of a
hydraulic press, the ram of which moves horizontally. The ram
has a steel rod extension passing through tho rear end of the
cylinder. Specimens for testing by tension have one of their ends
secured to this steel rod, and the other to the end of a scale-beam.
Specimens for crushing are placed at tho other end of tho cylinder,
and are compressed between the end of the ram and a crosshoad.
This crosshoad is attached to tho end of the scale-beam before
mentioned, by four powerful rods of steel surrounding the cylinder
and leading back to a crosshead attached to the beam. This latter
crosshead is detached from the beam when tensile experiments are
being made.

It will be obvious, on reflection, that when a piece is being crushed
by tho thrust of the ram, the four bolts sustaining the crosshoad
against this thrust must stretch in proportion to the power applied,
and hence the specimen will be moved bodily in the same direction,
and that this will affect tho accuracy of tho readings of tho mirror^
as it too will be moved horizontally with the specimen to which it
is attached. To correct this minute error in the readings, a second
mirror and scale are used to ascertain the extent of this horizontal
movement. The table holding this second mirror, against which
the little cylinder rotates, is secured to the frame of the testing
machine, which has no strain on it, and the little bar for rotating
the cylinder is attached to the crosehead; of course, any move-
ment of this head causes a rotation of the second mirror, by which
the extent of the movement can be at once ascertained.32

SUPERSTRUCTURE.

It is equally important to know the exact weight applied to the
specimen as well as the change of form assumed by it when subjected
to the weight. Having no faith in the accuracy and durability of
the ordinary mercury and spring gauges for such high pressures
as are required in a hydrostatic testing machine, I determined
that the absolute strain on the piece must be weighed on the
balance. This Col. Flad has very ingeniously accomplished by a
system of levers, balanced on hardened chrome-steel knife edges
and boxings, sufficiently powerful to stand a strain of one hundred
tons, and yet so delicate as to be turned by the weight of ono-half
of an ordinary cedar-covered drawing-pencil when placed in the
balance. One pound weight placed in the balance equals a ton of
two thousand pounds weight on the specimen.

I feel safe in asserting that the Company have a testing machine
which can scarcely be excelled in the accuracy, delicacy, and
minuteness of its results.

It has been placed in charge of Mr. Paul Dahlgren, C. E., by
whom a carefully tabulated record is kept of all tests made with it.
A great variety of these have already been made upon specimens
of steel, iron, woods of various kinds, granite, brick, limestone,
concrete, cement, models of tubes, trusses, &c., &c. Much valuable
information, having direct reference to the work in hand, has been
already obtained by these experiments.

SUPERSTRUCTURE.

On the twenty-sixth day of February last a contract was made
with the Keystone Bridge Company of Pittsburg for the construc-
tion and erection of the superstructure of your Bridge, including
that of the approaches. By. this contract the Keystone Bridge
Company undertakes to furnish all materials at the same prices per
pound and per foot at which they were estimated in my published
report of May, 1868, excepting cast-steel work, which is to be fur-
nished at ?20 per ton less than the cost sot forth in that report.
There will be about two thousand five hundred tons of steel used,
therefore the saving on this item will amount to about 850,000. The
contracting party will, however, recoive 840,000 more for erecting
the three spans than the estimate in the report. Every other item
of cost, as set forth in the report referred to, is the price per pound
or foot to be paid the Keystone Bridge Company. The amountsSUPERSTRUCTURE.

33

set forth under the head of engineering and contingencies, in that
report, and aggregating $149,512.14, for superstructure of Bridge
and approaches, are reserved by your Company, and will be ample
to cover any excess of materials required over the amounts esti-
mated, and for engineering expenses, &c.

By the terms of the contract with the Keystone Bridge Com-
pany, it agrees, under a severe forfeiture in case of failure, to com-
plete the structure, ready for use in all its parts, in seventeen
months from the time working drawings were furnished to it, pro-
vided it is not delayed by masonry work after the first of March
next. In case of such delay, the time of completion is to be ex-
tended no longer than the time it is so delayed. Completed work-
ing drawings wore not furnished until the first of July, as the
completion of certain parts of them was dependent upon data
that wore obtained from the testing machine, and which could
not be ascertained at an earlier period. This delivery of draw-
ings fixes the time for completion of the Bridge on the first of
December of next year. I have no apprehension that the masonry
will not be completed in season to prevent any claim for an exten-
sion of time on the part of the Keystone Bridge Company.

I have been informed that the Keystone Bridge Company has
contracted with the Wm. Butcher Steel Works Company, of Phila-
delphia, to furnish the cast-steel that will be required in the work.

Specifications for the cast-steel work will be found in the Appen-
dix to this report.

I have tested so many samples of steel made by this company,
which surpassed in strength the requirements set forth in theso
specifications, that I have no fear of its not being able to supply
the quality required. Several pieces of this steel have shown limits
of elastic reaction ranging from seventy thousand to ninety-three
thousand pounds per square inch.

Since my report, 1st May, 1868, in which the plan of super-
structure was described, I have made several modifications in the
general arrangement of the arches and in the details of their
construction, which will considerably improve the architectural
appearance of the Bridge and simplify its fabrication.34

SUPERSTRUCTURE.

These charges consist mainly in using hut one cast-steel lube of
eighteen inches diameter, instead of two of nine inches, in forming
the upper and lower members of each one of the four ribbed arches
composing each span; and in increasing the depth of each one of
the arches from eight feet to twelve feet from centre to centre of
these tubes.

The railways (which are below the roadway) are raised four feet,
so that in no place will they appear below the arches, as they did
in the original design. In that design the railways were eight feet
lower than the centre of the middle span. By deepening the arch
four feet and raising the track four feet, they are brought level
with the centre of this span, or above the soffit of the arch. The
lower ribs, or tubes of the arches, spring from the piers at their
original level, consequently the arch has four feet less versed sine,
or rise, than before. To lessen the grade of the railways, it was
necessary that the tracks should descend each way from the centre
of the middle span. This would cause them to fall below the cen.
tres of the side spans, to avoid which the level of the springing of
these two spans has been lowered eighteen inches at each abut-
ment. That is, the ends of the arches of the side spans resting
against the abutment piers, will be eighteen inches lower than the
other ends which rest against the channel piers. These arches^
like the central ones, have four feet less rise than as originally de-
signed, and by lowering their shore ends as stated, an additional
gain of nine inches depression is obtained at their contres, by which
the gradients of the tracks are proportionately lessened towards
the ends of the Bridge.

Raising the tracks to the height of the centres of the arches
will unquestionably improve the appearance of the structure, and
it is generally conceded that the alteration in the level of the
springing of the shore ends of the side spans is likewise an
architectural improvement. The effect upon the eye caused by
it will be somewhat similar to that produced by the camber of the
Bridge.

Of course these changes involved the necessity of revising the
former investigations and results, so as to ascertain the difference
in the strains, and to determine the alterations required in the sec-
tional areas of the various members of the structure, when thus
modified. An entirely new set of detail and general drawings
were likewise required in consequence of these changes.WIDENING THE AVENUES TO THE BRIDGE.

35

The lithographic view of the Bridge in the Appendix is a very
correct representation of the structure as it has been definitely
determined upon and is now being constructed. This view also
shows the depth of the bed-rock at the site of the different piers,
and the depth of sand overlying it during ordinary stages of water.

CONDEMNATION OF LAND FOR APPROACHES.

Since my last printed report, the land required in Illinois for the
eastern approach to the Bridge has been obtained by condemnation
and paid for by the Company.

Judicial proceedings have been commenced in this State for the
condemnation of the requisite grouud for the approaoh on this side
of the river. About one-fifth part of that which will be required
has already been obtained by purchase. A commission has been
appointed by the court to fix the values upon the remaining pieces
wanted. No delay in obtaining possession of all the land required
is anticipated. Those matters are entirely under the control and
in the charge of the Executive Committee.

WIDENING THE AVENUES TO THE BRIDGE.

During the last session of the General Assembly of the State of
Missouri, a law was passed requiring an election to be held by the
citizens of St. Louis to decide upon the question of taxing the city
with a sum not exceeding $500,000, to defray the cost of widening
the streets leading directly to tho Bridge. This election was decided
affirmatively by a very handsomo majority. Steps have already
been taken by the Mayor of St. Louis, Hon. Nathan Cole, to carry
tho will of the people, thus expressed, into effect.

Washington avenue is the most centrally located avenue in St.
Louis, and is also one of the most beautiful. It runs nearly in the
direction of the Bridge, which is locatod at its eastern terminus.
By the Bridge this avenue is virtually extended across the Missis-
sippi river into the State of Illinois. The law referred to requires
this avenue, which is eighty feet wide, to be widened at Third
street, where the roadway of the Bridge begins, to 140 feet, and at
Fourth street to 117 feet.

Third street, which is intersected by the roadway of the Bridge,
is at this point only sixty feet wide, and immediately south of the36

CHANGES IN THE BED OF THE RIVER.

Bridge it is only thirty-eight feet wide. The law contemplates the
condemnation of the fronts of seven blocks on this stroet, three on
one side and four on the other side, so that it will be 116 feet wide
at the Bridge. This width will bo maintained throughout two
locks north, and one block south of the Bridge. From this latter
point it will be gradually narrowed from one hundred and sixteen
feet to seventy-six feet, in the length of the second block south.
Thence south, Third street is but forty or fifty feet wide. The
widening of Washington avenue will, however, afford easy access
to Fourth street, which extends southwardly from the Bridge a
mile or more in one uninterrupted width of eighty feet, by which
the southern travel will be conveniently accommodated. North of
the Bridge, Third street, or Broadway, as it is called, will afford
one grand highway, one hundred feet wide, to the northorn limits
of the city.

These improvements will no doubt be completed by the city
authorities as soon as the Bridge is finished. They will contribute
greatly to the appearance and beauty of it, and will vastly
promote the convenience of the public. The wisdom and liberal-
ity of those who voted in favor of providing these magnificent
highways to accommodate the vast tides of travel that will hereafter
flow to and from the Bridge, will be more fully appreciated when
the structure is completed.

CHANGES IN THE BED OF THE RIVER.

I think the propriety of placing the channel piers of the Bridge
upon the bed-rock can be no longer questioned, if we consider the
facts developed in sinking them. The remarkable scour of fifty-one
feet below low-water line made in the bed of tho stream at the
east pier, by the freshet of last April, is sufficient to prove that
the scour extends much deeper than was supposed to be possible
by many distinguished engineers. The depth of scour was
assumed by them as never exceeding thirty feet below low-water
mark. At more than twico this distance below low-water mark
(sixty-six feet), pieces of bituminous coal, as large as a cocoa-
nut, were found imbedded in tho sand at the site of the east pier.
This coal had evidently been mined by man, and had not been
carried any great distance by the current, as its surfaces were bril-
liant and the angles which had been formed by fracture were sharpCHANGES IN THE BED OF THE RIVER.

37

and perfect. From those facts it would seem evident that the
coal must have been carried by the current to where it was found,
after the era of steam navigation, as we have no knowledge of
stone-coal having been used on the Mississippi before that period*
These pieces of coal had doubtless been lost from some steamer
navigating the river above the city, and lodged whore they were
found during a deep scour, resulting from some unusual under-
current acting upon the bed of the stream. These currents, I
am convinced, extend to a greater depth in the winter season
than in time of floods, which occur in the spring and early in the
summer.

The channel opposite this city is very narrow, and during severe
winters it usually freezes over very firmly before many wider
places abovo are closed. From these open parts floes and fields
of ice float down and are driven undor the fixed and frozen crust
at this point. The floating ice, being lighter than the water,
occupies the part of the channel immediately beneath the frozen
crust and there stops, and as this engorgement in the narrow
channel is increased by constant accessions from abovo, the cur-
rent must be gradually forced deeper and deeper. In this way
it is not at all improbable that where these gorges occur in the
river, its sand deposit may be totally removed in mid-channel,
and the bed-rock exposed to the action of the current. When
this occurs, a continuance of the supply of floating ice soon
chokes the passage of the water between the rock and the gorged
ice, and thus a natural dam is created across the stream. Sudden
rises of the river abovo these gorges, attaining in a few hours
several feet in height, are not at all unusual on the Missouri and
Mississippi during severe winters. When they occur, the immense
pressure of the water finally sweeps away the obstruction, and
fills the open spaces in the river below, for miles distant, with
ice so discolored with river sediment as to be scarcely capable of
flotation, and giving ample evidence of its imprisonment beneath
the surface.

Col. Roberts found a bone in the sand within a foot or two of
the bed-rock, under the east pier. It is a part of the femur or
thigh-bone of an animal larger than man, and is not petrified;
from which fact I assume that it could not, probably, have been
in the place where it was found during any long poriod of time.

While on this subject I will state, as an interesting geological
fact, that a piece of the bed-rock was broken off in which is found a38

THE ICE-BREAKERS.

considerable amount of white coral. It appears on-the surface of
the piece, which is about three inehes thick, and extends through
it, appearing on the lower or fractured side. The walls of the
cells are incrusted with quartz, the crystals of which aro so minute
that they can only he seen through a lens.

Beneath the west pier logs partly charred were met with at
the depth of fifty feet below low-water mark. During the last
pumping of sand from the east air-chamber, eighty-four feet below
low-water mark, particles of charcoal were constantly discharged
from the pumps with the sand.

The bed-rock was found to be of dark-colored limestone or
marble of such close texture as to admit of a moderate degree of
polish. Its surface was worn smooth and covered with corruga-
tions of from three to six inches in size, evidently proving that it
had been exposed to the direct and constant action of the current,
probably at some very remote period.

THE ICE-BREAKERS.

The lateness of the season when the sinking of tho east pier
commenced, made it absolutely necessary to provide some adequate
protection for the requisite boats, machinery, &c., at tho site of
the pier, against the heavy floating ice which invariably makes
its appearance here during the winter. This floating ice fre-
quently attains a thickness of ten or twelve inches, and often
covers the entire surface of the river, moving along at the rate
of about three or three and a half miles per hour. In proportion
as the weather becomes more intensely cold, the volume of the
ice increases, and the rate of its movement decreases, until it
finally comes to a full stop, and then quickly freezes over, afford-
ing, even within a few hours afterwards, a safe highway across
for pedestrians. In a day or two later the frozen mass becomes
so strong as to support the largest and most heavily loaded
wagons.

The freezing over of the river at St. Louis is not, however, an
invariable rule, as it does not occur, perhaps, oftener than three in
every four years on an average. Last winter was fortunately an
exception to the rule. For several days, however, the floating ice
was so heavy and compact that it was with the utmost difficulty that
the most powerful steam ferry-boats, built expressly to meet suchTHE ICE 'BREAKERS.

39

contingencies, could force a passage through it. One or two trips
across during an entire day being all that they could accomplish,
frequent attempts in the meantime proving abortive.

To establish in mid-channel any temporary works to withstand
an element so apparently resistless, and of such exhaustless volume,
was an untried experiment on the Mississippi that presented several
very discouraging features. The two chief difficulties were, first,
to place any construction above the pior that would not be quickly
scoured out by the current; and second, to make such construction
so strong as to resist-the power of the ice to sweep it away. The
method devised by me to accomplish the desired result will be fully
understood by the following description :

About two hundred feet above the pier, at a point from whenco
the current would flow to the center of the pier, a pile was driven
which formed the apex of a triangular system of piles shaped like
the letter A. From this pile two lines of other piles were drivon
at distances of eight feet. These two lines extended down stream
to the distance of two hundred feet, and represented the two sides
of the letter A. At their lower extremities these two sides were
about one hundred and eighty feet distant from each other. The
triangle thus formed was filled in with other piles driven in trans-
verse lines, from side to side, at distances of about fourteen feet,
and the tops of the entire system were then thoroughly braced
together with hown oak timbers, ten by ten inches square, well
bolted to the piles, which were of cypress.

The water was from forty to forty-seven feet deep when this part
of the work was executed, and many of the piles were washed up
as the work progressed. It was difficult to drive them into the
sand more than twonty feet deep, even with a steam pile-driver of
3,500 pounds weight.

About fifty feet above this triangle was placed a clump of nine piles
driven close together, and this was encased in sheet-iron throughout
about twelve feet of its length, to prevent the ice cutting the piles.
About one hundred and fifty feet above this clump of piles, a large
iron pile, made of the shell of an old cylindrical steam boiler,
fivo-sixteenths of an inch thick, twenty-eight feet long, and forty-
two inches in diameter, was sunk nearly to its full length into the
sand vertically. From the middle of this iron pile twelve feet40

THE ICE-BREAKERS.

below the river bed, was attached, before sinking, a wire cable of one
and seven-eighths inches in diameter. This cable was led over the
clump of piles and firmly secured to it, and from thence it was carried
down to the apex ofthe triangular system below, where it was hauled
taught and securely fastened. The object of the rope was to aid in
holding the piles steady until the entire protective system was com-
pleted, and also to form a cutting edge on which the large floes of
ice could be raised and broken asunder before striking the works
below. To the triangular system of piles the caisson was secured,
and was held by it against the current until it entered the sand.

The iron pile was open through six feet of its lower part to form
a sand-chamber into which one of the sand-pumps was introduced
to withdraw the sand and permit it to sink. Above this chamber
the pile was filled with ore from the Iron Mountain of Missouri, to
insure its sinking in the sand. A central tube fourteen inches
in diameter, mado of an old boiler flue, enabled the sand-pump to
bo passed through the pile to the sand-chamber at the bottom, the
ore being contained in the annular space surrounding this tube.
The water was about thirty-five feet deep at the site of this pile
when it was sunk. After its lower end had penetrated to a point
about sixty-two feet below the surface of the water, and the cable
had been tightly stretched, fifty or sixty cubic yards of largo rubble-
stone were thrown in around the pile to protect it from scour.

After this work had progressed thus far, a subsidence of about
ten feet in the river enabled us to bolt on to each side of the
triangle of piles, about ten feet below their tops, a longitudinal
timber about ten inches square, running the entire length of the
system. These two longitudinal timbers placed near the surface
of the water, and well secured to the sides of the triangle, consti-
tuted hinges by which two enormous ice-aprons were attached, one
on each side, to the triangle.

The object of these aprons, which will be presently described,
was to present an inclined surface on each side of the triangle of piles
on which the impact of the ico should be received. Any obstruc-
tion opposing a vertical surfaco to the action of the ice would be
soon crushed to pieces or ground away, whereas by presenting an
inclined one, the ice would slide up on it and be broken to pieces,
and be thus made to pass off harmless from it just as the soil does
from the plowshare and mould-board.THE ICE BREAKERS.

41

To protect the piles from the scouring action of the current it was
necessary to provide some means of keeping the current from them.
To do this with broken stone would be very expensive as well as
unreliable, and would besides create an obstruction much larger
than the pier, which would be difficult and costly to remove after
the masonry was completed. By planking the ice-aprons down
their inclined sides to the very bottom of tho river, the current
could be deflected by them from the piles below, and the ice from
them above, and thus both objects be attained. This was done.

The ice-aprons were two hundred feet long and sixty feet wide.
It was necessary to place them beneath the water at an angle of
forty-five degrees, and with the lower edge or side of each resting
on the sand, and to make them of such strength as not only to
resist a powerful current, but also to withstand the great pressure
of the ice, which might, by the fluctuations of the stream, be made
to impinge as low down on their sides as to the middle of their
surfaces, as well as at twelve or fifteen feet above that point.

The frames of the aprons were made of strong squared oak
timber placed transversely at intervals of eight feet, so that the
upper end of each one of them would rest by the side of a pile, and
on the longitudinal timbers before mentioned. The transverse
timbers were each sixty feet long, and were held in place by three
equi-distant string pieces, each two hundred feet long, bolted
beneath them. Two of these skeleton frames were thus con-
structed on shore, abovo the works, and were launched with suffi-
cient pine timber beneath to float them. They were then towed,
one to each side of the pile structure, and the end of each trans-
verse timber on the side next the piles was placed on the longitu-
dinal timber or hinge before named and secured temporarily to
them by chains. Tho outer edges of these frames were then secured
to barges placed alongside of them, and the pine floats under the
frames were then taken out. In this position, as the two frames
la£ on the water, they were planked with three-inch oak plank.
On that part where the ice was expected to impinge, No. 16 sheet-
iron was placed over the planking. A space on each apron about
twelve feet wide and extending their entire length was thus
covered with iron. Below this iron covering some openings were
loft through the aprons for the current to pass, to prevent the
formation of a bar of sand below the structure in the eddy that
would be created by the ice-aprons, after they should be in place.42

THE ICE-BREAKERS.

"When the aprons were both completed, the lines holding up their
outside edges at the barges were simultaneously cut away; these
edges then quickly disappeared boneath the current and were
swept by it to the bottom. Both aprons assumed the desired
angle. The upper extremities of the transverse timbers forming
them then rested upon the longitudinal timbers forming the hinge
by which their lower ends were rotated down to the bed of the
stream. The upper ends of these transverse timbers were then
each bolted to its respective pile, and that portion of the sides of
the pile system extending vertically above the aprons was planked
with two or threo strakes of ten by ten oak timber, at the part
nearest the aprons, and above that point with lighter oak plank.
At the apex of the breakwater thus formed, about one hundred and
fifty cubic yards of rubble-stone were thrown in, to thoroughly
close any space left between the upper ends of the two aprons.

This structure sufficed to completely turn the ice during the
winter, and made a thorough protection to the works and barges
about the pier. A deposit of sand rapidly formed behind the ice-
aprons which gave great support to them, whilst they in turn pro-
tected this deposit, once formed, from the action of the current.

Before our magnetic telegraph was erected, the ice was so heavy
for several days as to completely suspend intercourse between the
workmen at the pier and the shore. This contingency had been
provided for by provisioning the men with two weeks’ rations and
providing them with bedding.

During the greatest severity of the ice, Mr. McComas, who
remained at the pier, continued to operate, the sand-pumps, and
every morning and evening reported the progress of the work in a
conspicuous place and in characters so large as to be read by tele-
scope from the shore. The closing sentence of the report was
constantly “ Ice-breaker all right.”

This structure was duplicated at the west pier with equally
successful results. Both ice-breakers are still standing, having
successfully withstood the April flood, which attained a height
of twenty-six and a half feet above low-water mark; and although
the current is much increased by them and the river scoured out
in proportion, the original angles assumed by the aprons seem to
be almost entirely unaltered.CONCLUSION.

48

CONCLUSION.

I avail myself of this opportunity to express my thanks to the
several gentlemen assisting me in the various departments of the
Engineer and Construction Corps of the Bridge, and to commend
them to the kind consideration of tho Companj*, for the faithful
and efficient discharge of the important duties assigned them.

Respectfully submitted.

JAMES B. EADS,

Chief Engineer.APPENDIX.

SPECIFICATIONS FOR CAST-STEEL WORK.

The steel shall be of the kind known in commerce as Crucible
Cast Steel. It will be required to stand the following tests, and
failure to stand any one of such tests will be sufficient cause for
the rejection of the piece.

The staves composing the tubes will be required to stand a
compressive strain of sixty thousand (60,000) pounds and a tensile
strain of fortj* thousand (40,000) pounds per square inch of section
without permanent set.

They must stand a tensile strain of one hundred thousand
(100,000') pounds per square inch without fracture.

The modulus of elasticity Bhall not be less than twenty-six
million (26,000,000) nor more than thirty million (30,000,000)
pounds. This variation should be avoided if possible; in which
case the lower amount will be preferable. If a variation occurs
in the modulus, bars having the same modulus must be selected
in making up the tubes, so that one side of a tube shall not have a
greater power of resistance than the opposite one. Those having
tho same modulus shall be placed in the same tube. Each bar
will be tested by the contractor, and the modulus stamped on it
by the Illinois and St. Louis Bridge Company’s Inspector.

The steel pins will be required to stand, without permanent
set, a tensile strain of forty thousand (40,000) pounds per square
inch and an ultimate tensile strain, without fracture, of one
hundred thousand (100,000) pounds. As it will be inconvenient
to test these pieces, the Engineer will require to have two or
more of them made in one piece, and of sufficient length to cut
from the middle or ends of the pioco a sample for testing. In
such case, failure of the sample will cause the rejection of the
entire piece.46

APPENDIX.

Bods, bolts, eye-washers, rivets, &c., will be required to bear
an ultimate tensile strain of one hundred thousand (100,000)
pounds per square inch without fracture, and forty thousand

(40.000)	pounds per square inch without permanent set; such
parts of the work will not be tested in tension beyond forty
thousand (40,000) pounds, sample pieces only being subjected to
ultimate tests. Such tests as in the judgment of the Engineer
or Inspector may be necessary to detect flaws or other imper-
fections, when the pieces can not be conveniently subjected to
trial in the testing machine, may be used, and any flaw or other
imperfection existing in any piece will be sufficient cause for its
rejection, if, in the opinion of the Engineer or Inspector, it is
injured thereby.

The one-quarter (I) inch plate-steel for enveloping the staves
will be required to have a resistance to compression and tension,
without set, equal to forty thousand (40,000) pounds per square
inch, and an ultimate tensile strength of one hundred thousand

(100.000)	pounds.

The staves must be so accurately formed that when six short
sections of the same bar two (2) inches in length are bound
together by an elastic hoop, they will fit accurately at the joints*
and form a true circle seventeen and a half (17$) inches outside
diameter. They must be as straight as it is possible to make
them without planing them.

Steel templates will be provided by the contractor, under the
direction of the Engineer, and will be verified and stamped by
the Engineer before being used. The various parts of the work
must be made to fit these templates with the greatest attainable
accuracy, and it will be the duty of the Inspector to reject any
piece which, in size and direction of its part-1, shows the least
imperfection.

All holes through the steel work must be drilled, and all bolts
turned, unless otherwise directed by the Inspector in writing.
Wrought-iron bands on tubes must be turned on the inside, and
faced on each edge, as shown in drawings, and must be heated
and shrunk on.

The steel pins will be accurately finished according to the draw-
ings. The central part, where it is reduced in size, will not require
turning off. The conical portions must be large enough to fillAPPENDIX.

47

tightly the holes in the tube couplings. The couplings for tubes
n^ay be of rolled steel. The portions next to the main braces of
the arch must be true and parallel, to insure accurate contact and
adjustment of the braces to them; but these surfaces and the out-
side of the couplings need not be finished work.

Tho surfaces of these pieces coming in contact with each other,
or in contact with all other parts of the work except the main
braces, must be accurately finished.

Pieces of the material of those couplings will be subjected to the
same test as the pins.

Only the six (6) bolts nearest tho center of tubes, extending
through and through, are to be put into them before erection. The
caulking of the iron bands on the tubes and the remainder of the
through bolts must be put in after the superstructure is erected.
Four (4) one and three-eighths (1$) inch steel bolts will pass
through the ends of each set of main braces, and will be tapped
into the tube couplings. This work must also be done after erec-
tion of superstructure; the object of theso bolts being to prevent
any movement of the braces around the pins and of the braces on
each other.

The tube envelopes must have their edges planed and brought
closely together, to insure accuracy of diameter of tubes, before
riveting on the butt straps. Theso latter will be caulked.

Each piece, after being examined and accepted by the Inspector,
is to be covered with a coating of paint or other material, as may
be directed by the Inspector, to prevent rusting.CHEMICAL TESTS OF GRANITE.



Capt. J. B. Eads, Chief Engineer Illinois and St. Louis Bridge
Company :

Sir : I have submitted the samples of granite to a series of
experiments, with a view of determining their capacity for the
absorption of moisture, the effects of the action of alternate
freezing and thawing, and their resistance to decomposing influ-
ences, with the following results.

The absorptive per cent., or the amount of water taken up by
one hundred parts by weight, was determined in each instance by
immersing the sample in boiling water for fifteen minutes, and
removing the superficial moisture before weighing:

	HED GRANITE.	GUAY GRANITE-
	Per cent, of	Per cent, of
No. Of	absorption in	absorption in
Experiment.	UK) parts by	100 parts by
	weight.	weight.
1	.194700	.341673
o	.189670	.341942
3	.233641	.345082
4	.253420	.351791
5	.275892	.364073
6	.233641	.351912
7	.195640	.342510
S	.194520	.3420S9
9	.194591	.341783
10	.194702	.341599
11	.194711	.341690
12	.194794	.341687

After the twelfth trial the absorptive percentage was found to
be constant, and therefore the absorptive power of the red granite
is determined to be .1947 of one per cent, in every one hundred
parts by weight, and the absorptive power of the gray granite is
.3418 of one per cent, in every one hundred parts by weight—a
difference of .1469 of one per cent, in favor of the red.APPENDIX.

49

The per cent, of loss was calculated from the effect produced by
the disintegrating power of the sulphate of soda whilst crystal-
lizing. A boiling saturated solution of the salt being used in
which each sample was immersed for fifteen minutes, and, when
taken out, the sulphate of soda was allowed to crystallize thor-
oughly, then the salt was washed out with boiling water and the
loss in weight noted.

No. of Experiment.	RED GRANITE.  Per cent, of loss in 100 parts by weight.	GRAY GRANITE.  1'cV cent, of loss in 100 parts by weight.
1 			566511				335821
2		4562S2					343314
3				524111					369341
4				614235					341107
5				767891* 				.'.	380140
0 			51321S				 344316
7				524106				339149
8		 .531620				338555
9						541510				336032
10 			559102				335619
11 				565901					335739
12 			506010				335793

After the twelfth trial the percentage of loss appeared constant,
being for the red granite .566 of one per cent., and for the gray
.3357 of one per cent., or in proportion of 88 (gray) to 147 (red)
as calculated from the specific gravities. The specific gravity of
the red granite being 2.62038, and the specific gravity of the gray
granite 2.64224.

The disintegrating effect of nitre was tried in the same manner.
The average loss of the red granite in five experiments was .5597
of one per cent., and the average loss of the gray granite was
.38994 of one per cent.

The great disparity between the absorptive and loss percentages
of the red granite is explained when the large size of the crystals
of quartz and feldspar composing it is taken into consideration;
the loss being due to the bodily separation of the c^stals from the
surface of the specimen. In a specimen, the surface of which
was ground, the loss by the disintegrating force of the above solu-
tions amounted to .3089 of one per cent.; and a hammered speci-
men, treated in like manner, lost .384702 of one per cent.

4

Loss partly mechanical, by handling.50

APPENDIX.

The gray granite further suffers a loss from the solvont action of
water alone. A sample of it immersed in distilled water for a
number of days, at the ordinary temperature, was found to give
to the distilled water traces of lime and the alkalies, and the bot-
tom of the vessel containing the water was covered with a delicate
layor of silica. This was not the case with the red.

The disintegration of granitic material may be produced by tho
agency of chemical change, which change is undergone by some
foreign substance accidentally present, such as iron pyrites, garnet
etc., or the disintegration by chemical agency may proceed through
the decomposition of the normal constituents, mica and feldspar.
The disintegration of a granite may bo safely assumed to com-
mence always in the chemical decomposition of tho feldspar when
foreign substances aro absent. The decomposition rtf the feldspar
may be offeetod in different ways : first, by water containing free
carbonic acid; second, by the action of sulphurous ‘acid; and
third, by water holding traces of alkaline or other substancos in
solution.

The red varieties of feldspar are less affected by these agencies
than the white varieties, since the red varieties contain a large
quantity of sesquioxide of iron, and in some cases the alumina
is altogether replaced by sesquioxide of iron; Whenever this
occurs the feldspar obstinately resists tho decomposing agencies
above recited.

The superior durability and resistance to chemical change of
granitic material containing the red varieties of feldspar, over that
composed of the white varieties of feldspar, is clearly shown in the
case of these two granites.

The red granite lost, after three days’ immersion in water con-
taining free carbonic acid, frequently renewed, .0913 of one per
cent, in one hundred.parts by weight; the gray granite, treated in
the same manner, lost .64087 of one per cent, in one hundred parts
by weight.

Treated with a weak solution of sulphurous acid for three days.
the red granite lost .1456 of one per cent, of its weight, and the
gray granite .4253 of one per cent, by weight. Exposed to an
alkaline solution for four days, the red granite lost .2287 of one per
cent, of its weight, and the gray granite lost .7349 of one per cent.APPENDIX.

51

of its weight. An atmosphere of carbonic acid or sulphurous
acid gas causes an appreciable change in the gray granite, whilst
it has apparently no influence on the red. In recording the results
of the examination the term “ granite ” has boon retained on
account of its familiarity and common application.

With a view of determining the joint effect of the mechanical
and chemical disintegrating agencies, the samples, after treatment
with carbonic and sulphurous acids and with alkaline solutions,
Avere again severally subjected to the action of boiling water (to
determine the increase or decrease of the absorptive per cent.),
and to the action of the sulphate of soda solution (to determine
the loss percentage).

After treatment with solution of carbonic acid, the absorptive
per cent, was found to average in the red granite .2037 of one
per cent., and in tho gray granite .6601 of one per cent, in
one hundred parts by weight; tho loss percentage averaging in
the red .53041 of one per cent., and in the gray .9764 of one
por cent. After treatment with solution of sulphurous acid, the
absorptive per cent, averaged in the red .2399 of one per cent.,
and in the gray .7731 of one per cent.; the loss per cont. in
the red was .68021 of one per cent., and in the gray .8999 of
one per cent.

After treatment with alkaline solutions tho absorptive per cent,
of tbe red granite averaged .21227 of one per cent., and of the gray
.38419 of one per cent.; the loss percentage being respectivel}’
.70121 and .97929 of one per cent.

The destructive forces, therefore, most to be feared are not
those of the rain and the frost, but tho acid-laden air of the
great city and the alkaline waters of the great river. These are
constant, those only periodical.

I am, very respectfully, your obedient servant,

FELIX McARDLE, M.D.

St. Louis, March 30, 1370.52

APPENDIX.

August 4, 1870.

Captain James B. Eads, Chief Engineer of Illinois and St. Louis

Bridge Company:

Dear Sir : It was a peculiar task with which you have honored
me by asking a chemical examination of several specimens of gran-
ite with a view to determine, as far as it could bo done, not only
their comparative value as a building material for the piers of the
bridge under your supervision, but especially whether or not they
might equally and successfully resist the decomposing influence of
an atmosphere impregnated, like ours, with the smoke and gases
produced by the combustion of the vast amount of fuel consumed
in a city of such dimensions as St. Louis has already acquired, and
which will continuo to increase with her manufacturing interests.

Would it be possible to arrive, by experiments of but a few weeks’
duration in the laboratory, and by the aid of chemical reagents, at
a result in any degree similar to the slow but steady and continu-
ous action of the combined influences of moisturo, change of tem-
perature, the mechanical force of wind and rain, and the obnoxious
and deleterious gases which are engaged incessantly in the immense
laboratory of nature in producing the final decomposition of all
matter? It was obvious that if chemical researches would yield any
results at all, they could be only approximate, and would have to
be produced by substituting for the slow action of time, the strong
and immediate influence of the same or similar forces as act in
the atmosphere, but in a moro concentrated form, which, although
they could not insure precisely the same condition of things, would
at least test the resisting power of the materials to which they were
applied. With such reflections I commenced my investigations.

There was a considerable ditferor.ee in tho oxternal appearanco
of the three specimens; while the Richmond granite, with its fine
grain and smooth appearance, seemed to be suitable almost for
fine works of architecture, it shared with the granite from Maine
only the similarity of its gray color; for the structure of the latter
was much coarser, resembling in this respect more tho sample
from the Iron Mountain, which again differed from it widely in
regard to its pinkish color. The firmness and compactness of
the rock seemed to be the same in the threo samples, which were
broken up into small pieces of about two square inches each, and
thus exposed to the action of the roagents, the result of which is
hereby submitted to your consideration.APPENDIX.

53

Although the rock of the piers will never be oxposed to the
action of acids, I thought it would manifest at least its quality, if
their influence upon it should be ascertained, and consequently
immersed a piece of each separately in diluted muriatic, nitric, and
sulphuric acids. After ten days’ immersion, they were examined
and found unaffected; then they were boiled in the same solutions
for about an hour, replenishing the evaporated water. After cool-
ing, no visible change could bo discovered on either pieco, nor did
its strength seem to bo the least impaired; the romaining liquor,
however, from the Iron Mountain granite, contained iron, which
must have been uniformly dissolved from its surface, for the rock
was apparently as firm as ever, and even stood well the following
accident: IVhile ono of its specimens was being boiled with diluted
nitric acid, it became accidentally neglected, the liquid evaporated
entirely and left the granito dry and hot; but, nevertheless, its
surface remained intact, and even its sharp corners had retained

their firmness.

\

I had received but a small quantity of Maine granito, barely
sufficient for the foregoing experiments; it could not, therefore, be
included in the other series of tests.

In order to determine the probable action of the gases produced
by the combustion of fuol, which are mostly sulphurous and car-
bonic compounds, several pieces of each specimen of granite wero
treated with a slow current of a mixture of street gas, sulphurous
acid, carbonic oxide, and carbonic acid; and as it is recognized in
nature that moisture increases the force of the most powerful agen-
cies for decomposition, it was believed that the destroying efficacy
of these gases would also bo increased by keeping the rock moist
during the whole process. This experiment was continued for
nearly two weeks, and when the specimens were taken from the
apparatus their surfaces wore closely examinod, but no sign of
decay was visible, nothing could bo discovered to indicate that the
adhesion of the component parts had been loosened and the validity
of the rock destroyed; its edges even remained firm and sharp.

In the foregoing experiments, the gases referred to were admin-
istered pure and without any admixture of.air, smoko, etc.; but as
it might be inferred that their action would bo modified when ap-
plied in the same state as they are discharged from the furnaces into
the atmosphero, I considered it my duty also to determine the con-
centrated action of such mixture. The best place for such a test
seemed to me the front of the flues of a boiler, through whicho4

APPENDIX.

the gases pass directly from the fire, with all the'smoke and
undecomposed air, and where the temperature rises and falls from
sixty to two hundred degrees and more, according to the amount
of fuol and the rapidity with which it is consumed. The speci-
mens intended for this test were put into a dish with water, and
then placed into the front of a boiler flue, so that all the smoke
and the gases had to pass over and touch and envelop them. The
water was allowed to evaporate and dry up occasionally before
being replenished, and the rock was thus exposed to all the imagi-
nable changes attendant on such a situation. On the expiration of
twelve days, the dish was removed from its position. The rocks
showod no signs of decomposition, and were hard and firm yet. It
must bo mentioned, however, that I succeeded in loosening a few
fragments from the edges of both samples, which, from all appear-
ances, seemed to have been disintegrated by the sledge when the
samplos were broken up into smaller pieces.

It remained yet to test the influence upon the samples of frost
and mild temperature. One piece of each granite was soaked in
water and then repeatedly exposed alternately to the low temper-
ature of a freezing mixture and the atmosphero of 55° Fahrenheit,
before they were placed into the dish in the flue, where they
remained several days. The treatment had made no apparent
influence upon the rock.

If you will now recapitulate and compare the results of the expe-
riments fully and minutoly described in the foregoing paragraphs,
you will find that there was no tost made which has not terminated
in favor of the resistive power of either specimen of granite
against the decomposing influences of reagents; and if any such
experiments and tests are of any value whatever, or give permis-
sion to draw conclusions in regard to the technical value of the
material experimented upon, it is manifested beyond a doubt that,
both specimens of granite from Eichmond, as well as from the Iron
Mountain, are capable of enduring and resisting the combined influ-
ences of all the deteriorating gases which may contaminate the
atmosphere of our city.

Hoping that the manner in which I have treated this matter will
meet with your approval, I remain most respectfully,

Your obedient servant,

ENNO SAN DEE.

(Signed)APPENDIX.

55

Xames of the Men who were Employed in the Caisson of the East Pier
from the time it entered the Bed of the River until it was filled with
Concrete.

JAS. DONNELLY,

B.	O’KEEFE,

F O R E M E X :

PETER WHITE,

C.	W. BROWN,

FRANK JORDAN,
JAMES LOVE.

MACHINISTS IN CHARGE OF THE PUMPS:

PATRICK GL1NN,	C. MALBIN.

lock-tenders:

II. J. HARVEY,

THOS. CAVANAUGH.

workmen:

W. BURNES,

JAS. LYONS,

W. S. HAWKINS,

P. McPIKE,

P. PETERSON,

JNO. FL1NN,

WM. McKENNA,
CHAS. WAGNER,
HENRY COOPER,
AUG. DONKA,

P. DUMAS,

P. GALLAGHER,
WM. FOSTER,
j. McDonald,
w. McCartney,
DENNIS McCARTY,
P. FORD,

ANDREW COOPER,
JAS. SHEEHAN,

JOHN WILEY,

WM. LOOMIS,
JOSEPH BOWERS,
ED. RAND,

M. IRWIN,

WM. LAFFERTY,
M. O’KEEFE,
FRANK SANFORD,
M. MEYERS,

WM. MURPHY,

M.	MCDERMOTT,

D.	FORD,

F. FORD,

D. BRADLEY,
LOUIS GIBELEIl,
A. DEFORNEY,

N.	NICHOLS,

CHAS. SHAFER,
WM. CONNERS.A. Cabins for operators of purchases.

JB. Pontoons.

F. Hydraulic Jacks for raising materials,
ft. Hire cable to support trawling purchases.

I. Hire hoisting ropes.

A . Traveling purchases.

M. Shafts for starting and stopping traveling purchases
J\f. Valves for hydraulic jacks tor raising <t lowering materials.
0 Air pumps.

P Engines to drive air pumps.

,.. iiJ f 7 ft \,e	:J • t6	p

Scaled of anlticli to the "Foot.

C0RSTRUCT10H works and tuAgitiitccnr

FOR SINKING CAISSON AND LAYING MASONRY OF THE EAST PIER OF THE ILL.& ST.LOUIS BRIDGE.

Jerries REacLs Engineer.

Q. Hose for supplying air

S. Screws to keep the caisson level before reaching sand.
W. Guide piles for caisson.

X Caisson.

Y Pipes for water to sand pumps.

Z. Trusses for guide piles.

AA. Mixing room.

BB. Office.

CC. Tram ways for cement and stone ears.

Th.ScKra3.er lith.ll^Chesrmt St.Stloxiis.'Mro.Plate 11.

Ordinary Waterline

l lii.p oi Sdndh.nJ



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A. Cast * Co. Cor. 3! & Walnut, Bt. Loins, Mo.

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—Extreme Highwater of 1844

_City Directrix

anETOKf-©? mm ipohb mm e^dss.iski

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SHOWING THE INTERIOR OF THE

AND THE WORKII'
ILLINOIS AN

M. N. PLATE. II a

MAIN ENTRANCE SHAFT AND AIRCHAMBER

G OF ONE OF THE SAND PUMPS.

D SAINT LOUIS BRIDGE.

JAMES B-. EADS, Chief Engineer.

« C

A. Airlocks
B . Archamber
C. Timbergirder
D . Discharge of Sandpump
E . Sandpumps
F . Main Entrance Shaft
G . Side Shafts
H. Iron Envelope
I . Bracing for Shell

LowwaterlinePlate H.a.

Pim ®EF ©AO§§i!ffl IF@G3 (M§T PD[IK

A.Gast HCo..St. Louis.Plate II

tc

bJ

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I. Main Shaft.

K.	Side Shafts.

L.	Pipes far -Air A SandPumps

M.	Iron Girders.

XX. Iron Deck.

0. Airlocks.

MEttm ft miast t

OF TllE ILLINOIS & ST. LOUIS BRIDGE.

P.	Airchamber.

Q.	Timber Girders.
A. Timber J)eck.
SS. Iron £nvelope.
T. Timber Sides.

James B.Eads Engineer.

■Vlat e IV.

EAosgora [f®b hast ^srratErair.

I Main Shaft
K Side Shafts

L Pipes for Air and Sand-Pumps
M Iron Girders
NN Iron Perk
0 Airlocks

P Airchamber
(X Timber Girders
R Timber Peck
SS Iron Envelope
T Timber Sides

JAMES B. EADS, Chief Engineer.

August G-ast A Co.,St.Louis.Plate V.

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K Side Shafts

L Pipes for Air - and Sand Pumps
M fron Girders
NN Iron Deck
0 Airlocks

P Airchamber
0> Timber Girders
R limber Deck
SS Iron Envelope
T Timber Sides

August Gast & Co.,St. Louis.PHOTOMOUNT

PAMPHLET BINDER

PAT. NO.
877100

Manufactured by
GAYLORD BROS. Inc.
Syracuse, N. Y.
Stockton, Calif.