Chapter I: Early Life (2)

_April 18_.--The faces are found extremely tender; but having
proceeded with great caution, no accident occurred. None, I feel
confident, would occur if all idea of piece-work were abandoned. It
always operates as a stimulant, a very dangerous one. Obliged to
drive on, on account of expense, we run imminent risks indeed for
it. That a work of this nature, under such circumstances, should be
thus carried on, is truly lamentable. It is obvious that the clay
we have above our heads has been broken, by the ground beneath it
running or breaking in upon us. We shall have to fight it out until
we have a stronger or thicker stratum of clay. Sad prospect indeed
it is for us!

_April 20_.--The ground at No. 1 broke in again, and occasioned
great delay. Some bones and china came down.

_April 22_.--The diving-bell being on the spot, and Isambard having
moored it over the shield, he and Gravatt[17] descended at thirty
feet water. They found the same substances which had come through
the ground into the Tunnel. When Isambard was in the bell, he drove
a strong rod into the ground. Nelson, who was in the frame, heard
the blows.

[Sidenote: A dreadful panic.]

_April 29_.--Ground improving as we advance; we are not, however,
free from danger: a dreadful alarm took place this morning. While
Isambard and Gravatt were at breakfast, the porter came running in,
and exclaiming, ‘It is all over! The Tunnel has fallen in, and one
man only has escaped.’ Gravatt was the first to get to the spot,
and found all the pumpers upon the floor of the shaft, all
stupefied with horror, though every one was there quite safe, and
no rush of water was heard. Gravatt and Isambard were soon in the
shield, where they observed that a small portion of clay had fallen
from the top on the top floor.

_May 8_.--At half-past three in the morning, an irruption took
place, bringing down the deposits of the bottom of the river--lumps
of clay, stones, bones, wood, nails, &c., &c., with water. The
pumpers and men on the stage (Irish) all ran away, some exclaiming,
‘The Thames is in! The Thames is in!’ Ball and Rogers stood to
their post, and soon stopped this most formidable attack.

_May 10_.--Great difficulties present themselves, that oppose our
progress; the chief, however, is the lodgment of water above our
heads. There it loosens the silt or sand, and runs out, leaving
cavities that cause the clay above to break, and run down in lumps
and disturbed streams. This is very awful! This opens the way for
the river.

[Sidenote: Consequences of want of care more terrific and
mischievous than any preceding ones.]

_May 12_.--In moving No. 6, they left by some unaccountable neglect
the top staves behind, and in that state two top polings were taken
down. The ground being very bad, and high water at the same moment,
the ground began swelling. Attention was called to several points,
and Gravatt continued in No. 6. He drew out at the front of the top
staves a shovel, and also a hammer, that had come through the
ground above. They are the same which Isambard left at the bottom
of the river, when he went down in the diving-bell.

[Sidenote: Triumph of the shield.]

_May 13_.--Notwithstanding every prudence on our part, a disaster
may still occur. _May it not be when the arch is full of visitors!_
It is too awful to think of it. I have done my part by recommending
to the directors to shut the Tunnel. My solicitude is not lessened
for that: I have indeed no rest, and I may say have had none for
many weeks. So far the shield has triumphed over immense obstacles,
_and it will carry the Tunnel through_. During the preceding night
the whole of the ground over our heads must have been in movement,
and that too at high water. The shield must have therefore
supported upwards of _six hundred tons_: it has walked for many
weeks with that weight twice a day over its head. What flippancy
and inconsistency in some individuals, who, without any knowledge
of the subject, without so much as examining the state of the work,
will without the least reflection and hesitation obtrude their
suggestions upon every case. What shallow conceit for such to
pretend they can know better than those that have already the
experience that must result from years of deep thought, from days
and nights of incessant attention; who have the advantage of the
combined talents of several ingenious men, who devote their
undivided study, the whole resource of their well-stored minds, to
the enterprise; and to add to this, the benefit of the skill of one
hundred miners and excavators. Among this class of men, some have
been employed in the most perilous enterprises, when each
individual must have acted upon his sole judgment, where, in fact,
there is no room for an engineer to instruct and direct their
efforts. How easy it is to attack everything, to detract from the
merits of the best plan. There is always some weak point which may
be open to the penetration of the shallowest mind. Then comes the
exulting expression, _That I always said would never do, &c.,_ and
all the consequences with it.

[Sidenote: How easy to detract.]

_May 15_.--The water increased very much at 9 o’clock. This is
_inquiétant_! My apprehensions are not groundless. I apprehend
nothing, however, as to the safety of the men, but first the
visitors, and next a total invasion by the river. We must be
prepared for the worst. I have had no rest for many weeks on this
apprehension. Should it occur we must make the best of it, by
improving our situation.

_May 17_.--There is no doubt of the ground having improved very
materially since last Saturday. Very cheering indeed.

_May 18_.--Visited by Lady Raffles and a numerous party. Having had
an intimation by Mr. Beamish of their intended visit, I waited to
receive and to accompany them, not only from the interest I felt at
being acquainted with Lady Raffles, but also from motives of
solicitude, knowing that she intended to visit the frames. Indeed,
my apprehensions were increasing daily. I had given some
instructions for enquiring where we could obtain clay, that we
should have some barges full of clay to be in readiness. I was most
anxiously waiting for the removal of the tier of colliers that was
over us, being convinced that we should detect some derangement
then. I attended Lady Raffles and party to the frames, most uneasy
all the while, as if I had a presentiment, not so much of the
approaching catastrophe to the extent it has occurred, but of what
might result from the misbehaviour of some of the men, as was the
case when the Irish labourers ran away from the pumps and the
stage. I left the works at half-past five, leaving everything
comparatively well: Mr. Beamish continued on duty.[18]

Mr. Gravatt’s account is as follows: I was above with I. Brunel
looking over some prints, Beamish being on duty. Some men came
running up and said to Isambard something I did not hear. He
immediately ran towards the works, and down the men’s staircase. I
ran towards it, but could not get down. I leaped over the fence,
and rushed down the visitors’ stairs, and met the men coming up,
and a lady, who I think was fainting. Met Flyn on the
landing-place, who said it was all over. I pushed on, calling him a
coward, and got down as far as the visitors’ barrier. Saw Mr
Beamish pulled from it. He came on towards the shaft walking. I
went up to him to ask him what was the matter. He said it was no
use resisting. The miners were all upon the staircase; Brunel and I
called to them to come back. Lane[19] was upon the stairs, and he
said it was of no use to call the men back. We stayed some time
below on the stairs, looking where the water was coming in most
magnificently. We could still see the farthest light in the west
arch. The water came upon us so slowly that I walked backwards
speaking to Brunel several times. Presently I saw the water pouring
in from the east to the west arch through the cross arches. I then
ran and got up the stairs with Brunel and Beamish, who were then
five or six steps up. It was then we heard a tremendous burst. The
cabin had burst, and all the lights went out at once. There was a
noise at the staircase, and presently the water carried away the
lower flight of stairs. Brunel looked towards the men, who were
lining the staircase and galleries of the shaft, gazing at the
spectacle, and said, ‘Carry on, carry on, as fast as you can!’ Upon
which they ascended pretty fast. I went up to the top and saw the
shaft filling. I looked about and saw a man in the water like a
rat. He got hold of a bar, but I afterwards saw he was quite spent.
I was looking about how to get down, when I saw Brunel descending
by a rope to his assistance. I got hold of one of the iron ties,
and slid down into the water hand over hand with a small rope, and
tried to make it fast round his middle, whilst Brunel was doing the
same. Having done it he called out, ‘Haul up.’ The man was hauled
up. I swam about to see where to land. The shaft was full of casks.
Brunel had been swimming too.

The first alarm, as I heard it, was as follows: Goodwin, in No. 11,
said to Roger, in the next box, ‘Roger, come, help me.’ Roger said,
‘I can’t, I have my second poling down, and my face will run in.’
In a little time Goodwin said, ‘You must come,’ which Mr. Beamish
directed him to do. Roger turned round and saw Goodwin through a
sheet of water. Corps, a bricklayer, went to help Goodwin: he was
knocked down. Roger made his way alone, calling to Mr. Beamish,
‘Come away, sir, ‘tis no use to stay.’ Roger saw Corps fairly
washed out of his box like a lump of clay.

Sir Isambard’s journal continues:--

_May 19._--Relieved as I have found myself, though by a terrible
catastrophe, of the worst state of anxiety, that which I have been
in for several weeks past, I had a most comfortable night. Isambard
and Gravatt descended with the diving-bell, and stood upon the
tails of Nos. 10, 11, and 12.

_May 20._--Having descended into the hole and probed the ground, I
felt that the staves were in their places, and that the brickwork
was quite sound. It is evident that the great hole has been a
dredging spot. A large mass of bags full of clay, and united
together with ropes, was let down. The Rotherhithe curate, in his
sermon to-day, adverting to the accident, said it was a fatal
accident, that it was but a just judgment upon the presumptuous
aspirations of mortal men, &c.! The poor man!

_May 23._--Went with the diving-bell to examine the ground and the
bags, which do apparently well, but it is working rather in the
dark. It cannot, however, fail of making a much better stratum than
that we had before. The plan is therefore good.

On the 30th a raft was sunk over the shield, and the water in the shaft was brought so low that the last flight of steps was visible. However, on the next day the river broke in again; and as it was found that the raft was open at the west side, it was raised and towed on shore.

_June 5._--There is much danger in getting out of the diving-bell,
the bags are so loose in some places. One might sink and be
swallowed, which had very nearly happened to-day. Isambard and
Pinckney being down, the latter lost his hold. The footboard being
accidentally carried away, he could not have recovered himself had
not Isambard stretched out his leg to his assistance.

_June 17._--Visited by Charles Bonaparte. Isambard took him into
the arch with the yawl. Isambard fell overboard.[20]

On June 19, a general meeting of the proprietors was held, to consider the position of the company. Sir Isambard addressed the meeting, and also presented a long report, in which he entered very fully into the circumstances of the recent accident and the causes which led to it. He then described the means he had taken to restore the works by sinking bags of clay and gravel. He adds: ‘I have already succeeded in closing the hole through which the water first penetrated, and feel confident that the second opening which afterwards appeared is also stopped, but a short time is necessary to elapse for the new ground over the shield to settle and consolidate. It has already supported a head of water of thirty-five feet.’

_June 25._--At 7 P.M. made preparations to re-enter the shield.
Isambard, mustering the men who had been the last to quit the
frames, told them they would be the first to take possession of
them again--a precedence due, as he said, to them. Rogers, Ball,
Goodwin, Corps, and Compton, were accordingly ordered to trim
themselves for the expedition, provided with a phosphorus box, and
dressed in light clothes, to be fit for a swim.

At about ten o’clock, Isambard and Mr. Beamish, accompanied by Ball
and Woodward (miners), went down with the punt, and got to the
large stage, the head of the crane just emerging. It was found
impossible to get into the frames, as a mound of clay and silt
closed the entrance. The centering was in place and quite sound,
and of course the brickwork. Finding that they could not get
nearer, they gave three cheers, which were rapturously answered by
the men at the mouth of the Tunnel. Having placed candles upon the
ground that closed the entrance, and upon the head of the crane,
they returned. Isambard, having promised that the men who had left
the frames last should be the first to re-enter, returned with
them. This is a great day for our history!

_June 27._--Mr. Beamish was able to get to the frames, which he
found firm and undisturbed.

A small tarpaulin was now spread over the frames, and operations commenced for cleaning them. This was a most difficult and dangerous work, especially as the water was still so high that the frames could only be approached by boats. The men, even the best hands, were at first greatly alarmed at the danger they were in; but the example set by Mr. Brunel and Mr. Beamish produced, as Sir Isambard notes, the best effect, and they soon became reconciled to their situation.

_July 7._--Very uncomfortable in the frames; the candles cannot
burn, the ventilation cannot act. Isambard went several times
to-day down in the diving-bell. On one occasion the chain slipped
through the stoppers, but most providentially it jammed itself
tight before being altogether run out. _The consequence might
indeed have been fatal._ Can there be a more anxious situation than
that which I am constantly in? Not one moment of rest either of
mind or body. Mr. Beamish always ready. Poor Isambard always at his
post too, alternately below, or in the barges, and in the
diving-bell.

On July 11, Sir Isambard thought that matters had so far advanced that a large tarpaulin, which it was proposed to sink over the frames, ‘would have its full effect.’ It was accordingly sunk on the following day, under the superintendence of Mr. Brunel. Sir Isambard adds to his account of the operation--‘This reflects great credit on Isambard, and the apparent facility with which it was effected evinces his presence of mind, for a single _faux pas_ would have spoilt the whole.’[21]

_July 21._--During the early part of the night an alarm was given,
by Fitzgerald calling for clay wedges, and exclaiming that the
whole of the faces were coming in altogether. Rogers collected a
quantity of wedges to go to the frames, but no boat was to be seen.
He called to the men in the frames, but received no answer. Taking
the small boat in the east arch, he reached the frames, but found
nobody, nor any appearance of derangement in the ground.
Conjecturing they might be drowned, he explored further, and saw
the four men stretched on the small stage, not drowned, but sound
asleep!

_July 26._--Water nearly out of the arches. For the first time we
could walk to the frames--a most gratifying circumstance indeed!
_Two months and eight days._

_September 30._--How slow our progress must appear to others; but
it is not so, if it is considered how much we have had to do in
righting the frames and in repairing them; what with timbering,
shoring, shipping and refitting--all these operations being in
confined situations, the water bursting in occasionally, and the
ground running in: in short, it is truly terrific to be in the
midst of this scene. If to this we add the actual danger, magnified
by the re-echoing of the pumps, and sometimes (still more awful
warning!) the report of large pieces of cast iron breaking, it is
in no way an exaggeration to say that such has been the state of
things. Nevertheless, my confidence in the shield is not only
undiminished--it is, on the contrary, tried with its full effect,
and it is manifest now that it will soon replace us in good
ground, and in a safe situation. No top staves have given way. That
is our real protection.

_October 17._--At 2.15 A.M. Kemble, having first called upon
Gravatt, came to Isambard in a hurry, and, quite stupefied with
fright, told him that the water was in. Says Isambard--‘I could not
believe him. He said it was up the shaft when he came. This being
like positive, I ran without a coat as fast as possible, giving a
double knock at Gravatt’s door in my way. I saw the men on the top,
and heard them calling earnestly to those whom they fancied had not
had time to escape. Nay, Miles had already, in his zeal for the aid
of others, thrown a long rope, and was swinging it about, calling
to the unfortunate sufferers to lay hold of it, encouraging and
cheering those who might not find it, to swim to one of the
landings. I immediately, I should say instantly, flew down the
stairs. The shaft was completely dark. I expected at every step to
splash into the water. Before I was aware of the distance I had
run, I reached the frames in the east arch, and met there
Pamphillon, who told me that nothing was the matter, but a small
run in No. 1 top, where I found Huggins and the _corps d’élite_.
They were not even aware that any one had left the frames. The
cause of the panic was one of the labourers; hearing the man in No.
1 call for Ball, he ran away, jumping off the stage, crying, “_Run,
run, murder, murder; put the lights out._” His fellow-labourers
followed like sheep, making the same vociferations.’

_November 10._--Isambard gave his entertainment to nearly forty
persons, who sat at table in the Tunnel. Nothing could exceed the
effect for brilliancy. About 120 men partook of a dinner in the
adjoining arch.

As the year drew to a close, the difficulty of working the silt increased, and with this difficulty increased also the expense of maintaining the staff of men required. On December 18, Mr. Brunel, writing for his father, who was absent from town for a few days, thus describes the nature of the soil through which they were then passing.

The state of the ground over Nos. 1, 2, and 3 top has caused
considerable delay, particularly this week, although not such as to
give any cause of anxiety as to our future rate of progress, or to
have any serious effect except the increased expense incidental to
this delay. My father desired me to describe to the Board the
causes of these difficulties. There is a considerable spring at
this point, and a corresponding soft part in the bed of the river,
which seems to indicate the rising of the spring. The ground in the
neighbourhood is affected by this spring in rather a peculiar
manner: at the half-flood tide the pressure is greatest: dry hard
clay oozes with great force through openings hardly observable, the
silt and water running by starts. At high-water the pressure and
quantity of water begin to diminish and on the ebb-tide the ground
is hard and dry, and can be worked with ease. On the flood-tide
there are as many as twelve and fifteen of the best hands, besides
myself (or one of my assistants) and the foreman, engaged entirely
at one face.

On January 1, 1828, Sir Isambard returned to London; and on the 12th, when about 600 feet of the Tunnel had been completed, a second irruption occurred, which put a stop to the works for seven years.

The particulars of this accident are thus described by Mr. Brunel, in a letter to the Directors of the Company:--

I had been in the frames (shield) with the workmen throughout the
whole night, having taken my station there at ten o’clock. During
the workings through the night, no symptoms of insecurity appeared.
At six o’clock this morning (the visual time for shifting the men)
a fresh set or shift of the men came on to work. We began to work
the ground at the west top corner of the frame: the tide had just
then begun to flow; and finding the ground tolerably quiet, we
proceeded by beginning at the top, and had worked about a foot
downwards, when on exposing the next six inches, the ground swelled
suddenly, and a large quantity burst through the opening thus made.
This was followed instantly by a large body of water. The rush was
so violent as to force the man on the spot, where the burst took
place, out of the frame (or cell) on to the timber stage behind the
frames. I was in the frame with the man, but upon the rush of the
water I went into the next box (or cell), in order to command a
better view of the irruption, and seeing that there was no
possibility of then opposing the water, I ordered all the men in
the frames to retire. All were retiring, except the three men who
were with me, and they retreated with me. I did not leave the stage
until those three were down the ladder of the frames, when they and
I proceeded about twenty feet along the west arch of the Tunnel. At
this moment the agitation of the air, by the rush of water, was
such as to extinguish all the lights, and the water had gained the
height of our waists. I was at that moment giving directions to the
three men, in what manner they ought to proceed in the dark to
effect their escape, when they and I were knocked down, and covered
with a part of the timber stage. I struggled under water for some
time, and at length extricated myself from the stage, and by
swimming and being forced by the water, I gained the eastern arch
where I got a better footing, and was enabled by laying hold of the
railway rope, to pause a little, in the hope of encouraging the men
who had been knocked down at the same time with myself. This I
endeavoured to do by calling to them. Before I reached the shaft
the water had risen so rapidly that I was out of my depth, and
therefore swam to the visitors’ stairs, the stairs for the workmen
being occupied by those who had so far escaped. My knee was so
injured by the timber stage that I could scarcely swim, or get up
the stairs, but the rush of the water carried me up the shaft. The
three men who had been knocked down with me were unable to
extricate themselves, and I am grieved to say, they are lost; and I
believe also two old men, and one young man, in other parts of the
work.

This statement Sir Isambard embodied in a report to the Directors of January 28, which was circulated among the proprietors.

As soon as the first excitement caused by the irruption had ceased, Mr. Brunel directed the diving-bell to be prepared in order to ascertain the state of the shield and the extent of the disturbance of the bed of the river caused by the rush of water into the Tunnel.

He was, however, so seriously injured that he could not actively superintend the preparations, but his orders were given with his usual clearness, calmness, and decision; and as soon as the barge containing the diving-bell was properly moored over the Tunnel, he was carried out and laid upon a mattress on the deck of the barge, that he might direct what was to be done.

As evening came on he became so much worse that he was taken into the cabin; but everything which took place was reported to him.

At length, the bell being ready, it was lowered early on the Sunday morning, but the chain not being long enough, proceedings were delayed until a longer chain could be obtained.

As, however, a chain of the right size and length could not be obtained, the strongest cable which could be procured in the neighbourhood was substituted for the chain. A controversy then arose between the assistant engineers and the foremen as to the sufficiency of the strength of the cable; and it was agreed to consult and to abide by the opinion of Mr. Brunel, who was then lying in great pain in the cabin.

No answer could be obtained from him for some minutes, and then he only said, ‘Don’t go down.’ This not being satisfactory to the advocates of the sufficiency of the cable, it was agreed to lower the bell empty, which was done, and it was brought up safely; but just as it was swung over the barge, the rope broke and the bell fell on to the stage.

The next day Mr. Brunel was taken home, when it was found that, besides the injury to his knee which he received while endeavouring to save the lives of the three men who were with him,[22] he had received serious internal injuries, which kept him under medical treatment for several months.

When he was able to return to Rotherhithe all hope of continuing the works was for the time abandoned. When they were resumed, in 1835, he was entirely engrossed in the independent pursuit of his profession; and, with the exception of a few occasions when he acted for his father, he had no further connection with the Tunnel.

It is not, therefore, necessary to continue the narrative in detail; but a brief summary of the subsequent history of the enterprise may be interesting to those who are unacquainted with it.

The Tunnel was cleared of water, and efforts were made, unfortunately without success, to raise funds for the completion of the undertaking. Great enthusiasm was exhibited by the general public and by many eminent persons, including the Duke of Wellington; but the money was not forthcoming, and nothing was left but to brick in the shield, and wait for more favourable times.

It was not till the beginning of 1835 that the Company was able, by the aid of a loan from Government, to recommence the works. The old shield was removed and a new one substituted, in which considerable improvements were introduced. Slings connecting the frames were added, which enabled each frame to support its neighbours when necessary, and important alterations were also made in the arrangements for keeping the frames at the right distance from one another, and for giving greater facility of adjustment to the various parts.

Before the Wapping side was reached there were three more irruptions of the river, namely, August 23, November 3, 1837, and March 21, 1838; but in October 1840 the shaft on the Wapping shore was commenced. It differed from the Rotherhithe shaft, in being sunk the whole depth without underpinning, and was made of a slightly conical form, to reduce the friction in sinking, and had a larger quantity of iron hoops introduced into the brickwork, in order to increase its strength. When this structure had been sunk to the required depth (70 feet), the excavation of the Tunnel was resumed, and at last the shield was brought up to the brickwork of the shaft. The operation of making the junction between the Tunnel and the shaft was one of much difficulty, but it was at length satisfactorily accomplished, and the Tunnel was opened to the public on March 25, 1843--eighteen years and twenty-three days after the commencement of the work.[23]

Sir Isambard Brunel, whose health had for some time been failing, now retired altogether from his professional labours. After passing a few years in peaceful and happy seclusion, surrounded by those he loved, and watched over by their affectionate care, he died on December 12, 1849, in his 81st year, having been spared to carry to completion his greatest work, and to see his son following in his footsteps with a success which must have exceeded his most sanguine expectations.

* * * * *

The education Mr. Brunel received from his father was well calculated to form the foundation of his future career. During the later and more arduous part of the contest, which was ended by the irruption of January 1828, he held both the nominal and actual post of Resident Engineer of the Thames Tunnel; but from the commencement of the works, when he was only nineteen years old, he had been, as stated by Sir Isambard, ‘a most valuable coadjutor in the undertaking.’ While placed in this responsible position he acquired habits of endurance and of self-reliance, and learnt to act with promptitude and decision in the application of those measures which experience had shown to be effective in each particular class of emergency. But beyond all other advantages, he had before him the example of his father’s character, in which a rare degree of gentleness and modesty of disposition was joined to unflinching energy, and a determination to overcome all difficulties.

NOTE A (p. 5).

_The Bourbon Suspension Bridges_.[24]

The suspension bridges designed by Sir Isambard Brunel for crossing rivers in the Ile de Bourbon were two in number. One of them had two spans of 122 feet each in the clear, and 131 feet 9 inches between the points of suspension of the chains. The second had but one span of the same dimensions as those of the larger bridge. In the design of these bridges one of the most important points to be attended to, was to render them secure against hurricanes, which are both frequent and severe in the Ile de Bourbon.

In the larger bridge there was a pier of masonry, built in the middle of the river up to the level of the roadway of the bridge. The suspension chains of the bridge were in three groups, 9 feet 8 inches apart, so as to leave room for two roadways, each about 8 feet 9 inches wide. Each of these groups of chains consisted of two chains side by side. Each chain was made with long links like those of the chain cables used for moorings.

These links, which were made of iron 1·36 inch in diameter, were 4 feet 8 inches long, inside measure, and were each connected together by two short coupling links, 8¾ inches long, inside measure, of iron 1·36 inch by 1 inch, and two pins, each two inches in diameter.

The two chains of each group were placed side by side, with the links upright; one of the pins at each joint was made long enough to serve for both chains, and, in the middle of its length between the two chains, was passed through an eye at the upper end of one of the suspending rods of the bridge. Thus to every joint in each group of the main chains, or at intervals of about 5 feet, there was a suspending rod. These rods were 1¼ inch in diameter.

The pins of the joints of the main chains had half heads at each end of them. They could thus be easily inserted in erecting the bridge, but once in place were quite secure. At every fourth joint in the main chains one of the joint pins was made in two halves, with wedges inserted between them for adjusting the length of the main chains.

Thus there were six chains, and as the links of these had each two parts of iron 1·36 inch in diameter, the total sectional area of the six chains was 17·4 inches.

Each group of the main chains was supported at a height of 25 feet 6 inches above the roadway at the centre pier, and at a height of 5 feet 3 inches at each of the side piers, the lowest portion of the curve of the chain being about 1 foot below the points of suspension of the side piers.

The upright standards, carrying the chains both at the centre pier and at the side piers, consisted for each group of chains of a triangular framework of cast iron, strengthened by long bolts of wrought iron. There were thus three of these triangular frames parallel to each other at each of the piers, and those at the centre pier were braced together over the carriage road. The main chains were not bolted to the standards, but were slung from them by a vertical suspension link, which thus allowed them to move a little lengthways. This link, in fact, performed the function of the rollers now generally put under the saddles of suspension bridges.

The ends of the main chains were held by back stays, formed of bars 3 inches broad by 1¼ inch thick, and 10 feet long, with joints made with short links, and 2⅜ inch pins. The ends of those back stays were secured to holding down plates 3 feet in diameter, sunk deep in the ground and well loaded.

As there was a vertical suspension rod at each joint of the main chains, there was a suspension rod hanging from each of the three groups of chains at about every five feet of the length of the bridge. To each set of these rods was attached a cross girder of cast iron of a =T= section, with a large rounded bead at the lower edge of the upright web; and connecting these under each of the main chains was a longitudinal timber beam about 8 inches square.

The cast-iron cross girders carried longitudinal teak planking, the planks on which the carriage wheels ran being 12 inches wide and 4 inches thick, protected at the top by wrought-iron plates running longitudinally. The horse-path was protected by iron plates arranged crosswise.

Under each span of the bridge were four chains curved upwards and also sideways. These chains were fastened at their ends into the piers, and were connected to the roadway by ties drawn up tight and attached to the main longitudinal bearers of the platform; the object being to stiffen the platform.

These under tie chains were made each of a set of rods 1¼ inch in diameter with eyes at their ends, the ends being connected by short joint links and 1¼ inch pins; and to these joint links were attached the tie rods which connect these inverted chains with the platform of the bridge, and so prevented its being lifted or blown sideways by the force of the wind.

In the smaller bridge, which, as has been said, consisted of one span of 131 feet 9 inches between the points of suspension, these points were 15 feet 5 inches above the roadway, and the lowest part of the chain was 9 feet 7 inches below the points of suspension. The details of this bridge were similar to those of the larger one.

NOTE B (p. 5).

_Experiments with Carbonic Acid Gas._

In 1823 Mr. Faraday made the important discovery that under certain conditions of temperature and pressure many gases could be liquefied, and that these liquids exerted great expansive force by slight additions of temperature, returning quickly with regularity and certainty to their original state upon the application of cold.

The discovery of this new force appeared of such importance, that Mr. Faraday lost no time in publishing it to the world; and Sir Isambard Brunel very soon afterwards commenced a series of experiments to determine the value of the liquid gas as a mechanical agent.

The first experiments were made at Chelsea; but the prosecution of them was soon transferred to the care of Mr. Brunel at Rotherhithe, where he devoted all his spare time to the construction of his father’s proposed ‘Differential Power Engine.’

That the progress of this discovery, and of the experiments made with a view to the application of the liquid gas, as a motive power, may be understood, it is necessary to state that in March 1823 Mr. Faraday communicated to the Royal Society the results of his first experiments on the liquefaction of gases.

The fluid was then produced by the decomposition of the hydrate of chlorine by heat in a closed tube, the amount of gas evolved being so great as to produce a pressure in the tube sufficient to condense the gas into a fluid of the same volume.

This interesting experiment was followed by others with that rapidity and success so remarkable in everything undertaken at that time in the laboratory of the Royal Institution; and within a month another paper was read before the Royal Society, in which the degrees of pressure and temperature at which several gases could be liquefied were recorded, and the means employed to produce and liquefy each gas accurately described.

On April 17 a third paper was communicated by Mr. Faraday, ‘On the Application of Liquids produced by the Condensation of Gases as Mechanical Agents.’

The question is thus stated: ‘The ratio of the elastic force dependent upon pressure is to be combined with that of the expansive force dependent on temperature; and the development of latent heat on compression and the necessity of its reabsorption in expansion must awaken doubts as to the economical results to be obtained by employing the steam of water under very great pressures and very elevated temperatures.

No such doubt can arise respecting liquids, which require for their existence even a compression equal to thirty or forty atmospheres, and where slight elevations of temperature are sufficient to produce an immense elastic force, and where the principal question arising is whether the effort of mechanical motion is to be most easily produced by an increase or diminution of heat by artificial means.’

Difficulties were suggested by Mr. Faraday as to the possibility of obtaining sufficient strength in the apparatus, but the small difference of temperature required to produce an elastic force of many atmospheres, he considered would render the risk of explosion small.

To construct the machinery whereby this new force could be practically applied as a substitute for steam, occupied the time of Sir Isambard Brunel and his son at intervals for several years; for although Mr. Brunel was satisfied at an early period of the enquiry that the liquefied gases could only be advantageously employed where the cost of motive force was secondary to economy of space and to the avoidance of the cumbrous apparatus required for the use of steam, still he was so impressed with the importance of the subject, if the difficulties he foresaw in its application could be overcome, that he continued his experiments for a long period with unflagging energy and perseverance.

The facts relating to the liquefaction of the gases, their elastic force when liquefied under different temperatures, the rapidity with which they could be alternately expanded and condensed, and the best mode of producing each gas, were determined by Mr. Faraday; and as Mr. Brunel was at that time attending the morning chemical lectures at the Royal Institution, he was in constant communication with him, and thoroughly conversant with his experiments.

After Mr. Brunel had made a few preliminary experiments, Sir Isambard determined to employ liquefied carbonic acid gas for the motive power of the proposed new engine, the facility and cheapness of its production, its great expansive force, and its neutral character distinguishing it from any other gas; but it was long before vessels were constructed, in which gas could be produced in sufficient quantity and purity to exert the force required to liquefy it in its own volume, for it was soon found to be impossible to obtain the required pressure with pumps.

Carbonate of ammonia and sulphuric acid were the elements used, and the generator was so arranged that it could be charged, emptied of atmospheric air, and the joints made perfect, before the commencement of the formation of the gas which was to be liquefied.

To the generator was attached a receiver, which could be surrounded with a freezing mixture, so that the temperature of the gas in the cylinder might be below that in the generator.

The gradual formation of the liquid, the development of its elastic force, and the regularity and rapidity with which it increased or diminished by each degree of heat or cold, were carefully watched through a glass gauge, and the receiver when filled with liquid could be disconnected from the generator.

The mechanical difficulties as they arose, one after the other, in the construction and arrangement of the various parts of the generator and receiver were at length overcome; and the receiver was not only filled with liquid gas, but found to be capable of retaining it, whether exerting an elastic force of 30 atmospheres at ordinary temperatures, or of 100 atmospheres when subjected to a slight degree of heat.

The receiver being satisfactorily completed, the next object of attention was the design and construction of a working cylinder capable of resisting at least 1,400 lbs. pressure on the square inch; a task which was one of great anxiety, as any weakness might have caused a serious accident.

It was only after the trial of every known method of making joints to resist high pressures had failed, that an arrangement was devised, requiring the most perfect workmanship, by which packing of any kind was dispensed with, and the cylinder fitted for use.

With the improved tools of the present day it is not easy to realise the difficulties, delays, and disappointments which forty-five years ago occurred from the failure, first of one part of a joint, and then of another; but the construction of vessels capable of producing and also of retaining the gas in its liquid state, with the means of alternately expanding and condensing it from thirty or forty to eighty or one hundred atmospheres, having been accomplished, the object of the expenditure of so much labour and inventive power appeared to be within reach.

The construction of the machinery to utilise the elastic force contained in the cylinder was now proceeded with. Day by day new difficulties arose, and each as it was successfully met seemed but to leave another of greater importance to be surmounted.

It is not necessary in this Note to describe the various arrangements which were devised for transferring the great elastic force in the cylinder of small diameter to a piston in another cylinder of much larger dimensions; it is sufficient to say, that after the devotion of much valuable time extending over several years, and a very large expenditure of money, and after carefully considering the cost of the liquid carbonic acid gas, the difficulty of preventing waste, and the necessarily very expensive character of the machinery, Mr. Brunel was satisfied ‘that no sufficient advantage in the sense of economy of fuel can be obtained by the application of liquefied carbonic acid gas as a motive power’; but so thoroughly did he exhaust the subject before he committed himself to this opinion, that no one has since renewed the enquiry or attempted to make a machine to be moved by the elastic force of liquefied gases, the construction of which, it was well known, had baffled the inventive genius of Sir Isambard Brunel and his son.