The Thames Tunnel (continued)
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 masses. [marginal notes: 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. [marginal notes: 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 4½ 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 circumstance seems to warn one of the need of great vigilance and great prudence in the progress of the enterprise. [marginal notes: Cofferdam burst at Woolwich.] [marginal note: 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! [marginal notes: 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. [marginal notes: 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 quantity 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.