The life of Isambard Kingdom Brunel, Civil Engineer Part 2

[Sidenote: Unremitted attention wanted.]

_February 10_.--Went very early to the Tunnel for the purpose of giving directions to prop up the back of the staves, which, for want of weight at the new shaft, might be overbalanced by the pressure of the ground at the back. I could not rest a moment until it was done, for the consequences might have been fatal, at this moment in particular. What incessant attention and anxiety! To be at the mercy of ignorance and carelessness! No work like this.

[Sidenote: Observations on the mode adopted to check the water.]

_February 12_.--The ground having been opened carefully from under the curb of the pit [_see above on date February 3_], the greater part of the gravel was removed, and stiff clay subst.i.tuted for it. This was done by driving first some wrought-iron flat bars, which kept the ground up.

This shows that the shield is a most powerful protection, and would enable us to penetrate through a bed of gravel. Though the breaking in of the water had somewhat terrified the man in No. 5, he soon returned to his post, and the others have acknowledged their full confidence in the security afforded by the shield. The boring ahead had not yet been attended to: it is owing to the want of this precaution that this accident is chiefly to be ascribed; for had we known as much as we now do, we might have pa.s.sed through without the pit being opened.

_March 1_.--Water at the back of the frames, but less than before. The men show a great deal of spirit in overcoming the present difficulties.

Isambard was very busy yesterday and to-day in the frames, and about the works. He was severely hurt in the leg by a piece of timber falling against it. [_This accident prevented his attending again at the Tunnel until the 24th_.]

On March 6 the proprietors paid a visit to the Tunnel, and were highly satisfied with what they saw. On that evening Sir Isambard writes:--

It is of absolute necessity _now_ to provide for everything that is conducive to the more expeditious management of the frames, and to a greater facility in getting up the brickwork. If these two points are realized, then indeed we may soon expect to be moving at a good rate--not less than I have held out, namely, 3 feet per 24 hours.

[Sidenote: Water stopped as expected.]

_March 11._--Received early in the morning a report from Armstrong stating that the water was completely stopped--that it had been stopped during the night. Aware that we had pa.s.sed the gravel, it was of course expected that we were under the clay; means were therefore resorted to, to drive clay and oak.u.m at the tail of the top staves, which was productive of a very good effect. The great shield was soon entirely free of water. This shows the efficiency of the shield to oppose difficulties which could not have been overcome without the complete protection it affords, under almost any circ.u.mstances. Indeed this has been a tedious operation since January 25, when the water first burst upon No. 5, at the front of the shield. The miners as well as the bricklayers have worked with great spirit and perseverance through the whole, during a period of 44 days. The well that was made at the front of the shaft has been of use in acquainting us with the extent of the open ground we had to pa.s.s through. It will be made a useful opening for ventilating the works. By means of this well we have been able to apply the lead pipes with which the water has been diverted: it is not therefore a useless expense. Things were put in better order to prepare for a more expeditious way of working. Directions were given to place the frames in a better condition. Isambard is still too unwell to go to the Tunnel.

[Sidenote: Considerable slip of ground: how to check it.]

[Sidenote: Very dangerous.]

_March 25._--Went to the Tunnel with Isambard. Found that a considerable fall of ground had taken place again at the right side. No one could account satisfactorily for it. I inspected it, and directed that, after making it good, flat bars of iron be driven at the head of the side staves, in order to pin it up, and in order to enable the miners to get at the solid ground. It is very bad and extremely dangerous; the ground is evidently the same as that which, in the report of the first attempt, was found so loose as to have dropped upon the works, leaving a large cavity above, when it is said the man ascended and made good the hole. We should be warned by this, lest we should meet another as fatal as it ultimately was on that occasion. [_This observation refers to the driftway of 1807._]

_April 24._--By Armstrong's report the water is entirely out, and the men at work in the morning in removing the dirt, &c. Isambard engaged at the Tunnel, where I am not yet able to attend as often as I could wish. Everything goes on well, much through his exertions.

_May 11._--One hundred feet will be completed to-night.

_May 22._--The top plate over the frame No. 1 has been cracked without any particular violence or stress. It appears that it is nothing but the change of temperature that is the cause of that rupture. The accident justifies the opinion I have of cast-iron not being safe upon traction, and the precaution of having had wrought-iron bolts at the back of the frames. [_These were vertical rods which took the tensional strain._] Without these bolts what would have become of the shield, if one casting was to break? The fracture was accompanied with a loud report like that of a gun.

Isambard was in the works at the time of breaking: nothing could have prevented it.

[Sidenote: The shield being too much out, resolved to move it bodily.]

_May 25._--I observed that nothing whatever had been gained to recover the deviation [_the shield had gradually worked 2 feet 3 inches to the westward_], which subjects us to so much inconvenience and loss of time. The only way to bring the shield right is by taking the frames sideways.

_June 3._--Finding it too laborious and almost fruitless to bring the frames in the right way, I came to the determination of having them brought bodily to the east by cutting the ground on the side.

I accordingly gave directions to Armstrong to proceed in making a heading out of No. 12, and by securing the side staves to continue downwards until the ground be clear. The working was accordingly discontinued in front.

_June 4._--The mode of proceeding by the common way of mining shows the impracticability of carrying a large excavation anywhere, particularly under a considerable body of water. The expense of timbering would be too great, even if it could be sound. The ground above the frames is remarkably good, but under it there is a stratum of silt which breaks and falls in large ma.s.ses.

[Sidenote: Isambard's service very important and most efficient.]

_June 5._--Isambard got into the drift, and gave the line for the better disposition of the staves, which was afterwards done in a proper manner. Isambard's vigilance and constant attendance were of great benefit. He is in every respect a most useful coadjutor in this undertaking.

_June 10._--The last frame (No. 1) is brought close to the others, and the brickwork brought up to fill the back.

[Sidenote: Dangerous state of the ground. Precautions taken.]

_June 15._--On inspecting the face of the ground this morning I observed a breach in the front of Nos. 3, 4, and 5, where the ground has given way in the lower cell. This was truly alarming. I ordered iron staves to each floor in order to pin the ground, and thereby to counteract the slipping which would immediately take place.

_June 19._--The bricklayers left off work, but, on enquiring into the cause, I learned there was no other but to have a libation upon the new arrangement of piece-work.

_June 29._--Gave positive directions to cut only 4 to 5 inches thick at a time at the front of the top cells, instead of 9 inches, as they had done for some time.

_July 3._--The great question is, does the clay undulate at its surface? We should have some reason to apprehend that it does so, because at the beginning we had not proceeded many feet into the clay when we struck again into the gravelly stratum. The surface of the clay must therefore have sunk at that particular spot; which circ.u.mstance seems to warn one of the need of great vigilance and great prudence in the progress of the enterprise.

[Sidenote: Cofferdam burst at Woolwich.]

[Sidenote: Warning for us.]

_July 10._--A cofferdam burst yesterday at the works at Woolwich, having blown up from the foundation. How cautious this should make our men! The cofferdam may be repaired, and very easily too, but an irruption into the Tunnel--what a difference, particularly at this early period!

[Sidenote: Carelessness of the miners.]

_August 10._--Found the lowest cell of No. 1 left by the workmen _without a single poling against the ground_. This is indeed a most unjustifiable neglect.

_August 12._--At six this morning completed 205 feet.

[Sidenote: Observations on the bad effect and consequence of driving on as is done.]

_August 21._--This piece-work has not been productive of much effect as to quant.i.ty of work. As to quality it is very questionable. A work of this nature should not be hurried in this manner. Fewer hands, enough to produce 9 feet per week, would be far better than the mode now pursued _from necessity_, but not from inclination on my part. Great risks are in our way, and we increase them by the manner the excavation is carried on. The frames are in a very bad condition.

_September 5._--It is much to be regretted that such a work as the Tunnel should be carried on by the piece. Obliged to drive on, no time is left to make any repair, or to recover any lost advantage.

Isambard is most active. Mr. Beamish shows much judgment in his exertions, and zeal in his attendance.[14]

[Sidenote: Water breaking in at back of frames.]

[Sidenote: How to check it. Isambard's exertions.]

_September 8._--About 2 P.M. I was informed by Munday that water was running down over No. 9. I went immediately to it. The ground being open, and consequently unsupported, it soon became soft, and settled on the back of the staves, moving down in a stream of diluted silt, which is the most dangerous substance we have to contend with. Some oak.u.m was forced through the joints of the staves, and the water was partly checked. Isambard was the whole night, till three, in the frames. At three I relieved him. He went to rest for about a couple of hours; I took some rest on the stage.

[Sidenote: Things improving.]

_September 9._--Towards noon the stream changed its character. The clay, being loosened by the water, began to run, but it thickened gradually. It was late in the evening before the loosened clay acquired the consistency of a loose puddling, which covered the staves, and made them a complete shield against further irruption, or rather, oozings of mud. If we consider that at this place we have at the utmost 9 feet between the top staves and the gravel, over which the river flows, it is most satisfactory and most encouraging to have this additional proof of the protection which the shield affords. At nine o'clock at night Isambard sent me word that 'tout va a merveille;' indeed it was so, for it was like a stopper interposed between the river and the top-staves. Instructed as the men were by the first accident, they went on as usual in the irrespective occupations. Pascoe, junr., and Collins were remarkably active and persevering, and some other men equally so; while old Greenwell encouraged them by a speech of his own in high commendation of the security of their situation.

[Sidenote: Water more abundant. Is it from the river?]

_September 12._--The water, bringing with it a sort of clay broken in small particles, increased to an alarming degree. In consequence of this continued displacement of the silt and clay, a cavity had been formed above the staves. At about three, when I had gone to the Court of Directors, the ground fell upon the staves with great violence, causing a surge most alarming as to probable consequences. Isambard was at that moment in the upper frames, and he gave directions for increasing the means of security. On my return I found things much worse than I left them, but every means of security was judiciously applied. During the night in particular things presented a very unfavourable appearance. The men, however, were as calm as if there were no other danger to be dreaded than wet clothes or the splashing of mud. I observed the men in the lower cells were _sound asleep_.

[Sidenote: Exertions by the men.]

[Sidenote: Slight improvement.]

_September 13._--Every means were resorted to in the course of the night and during the early part of the day to stop the water. The men have shown great zeal and good management in their respective avocations, and above all the utmost confidence. Isambard has not quitted the frames but to lay down now and then on the stage. I have prevailed on him to go to his bed, or rather, used my endeavours to induce him; but he has not since last Friday night (the 8th). Things were rather better at the close of the day.

_September 14._--Things upon the whole have a.s.sumed a more favourable aspect. The situation is nevertheless very critical.

Nothing but the utmost precaution in following up what has begun can bring us out of it. This has been a most eventful week!