488 Sir Frederick Bramwell ' [Feb. 22, 



for about 1050 feet from the Surrey sliore, and was then abandoned 

 in consequence of the inflow of water, and the want of funds. 



In 1826 the talented Marc Isambard Brunei commenced, from a 

 point a little to the east of Rotherhithe Church, the celebrated 

 Thames Tunnel. I have had lent to me by Mr. Law, who was an 

 assistant engineer in the carrying out of the Thames Tunnel, a 

 diagram of the work, as intended. It was proposed, that on each side 

 of the river there should be sunk a circular shaft 200 feet in diameter, 

 and containing a spiral roadway, having a rise of one in twenty-five, 

 by which vehicular traffic could ascend and descend. At the bottom 

 the roads were to pass across two other shafts, each of 50 feet 

 diameter, provided with staircases, for the foot passengers. The 

 tunnel itself had two separated roadways, with footways, and arches 

 of communication, from the one roadway to the other. There is no 

 doubt that this was a very wonderful work, and one that largely 

 occupied public attention. Forty years ago the particulars of its 

 construction were well known, and it would have been a waste of 

 time to have described them to an audience in this room ; but now 

 the details are forgotten, and I think that I may be forgiven if I 

 ask attention for a few minutes, while I relate how the work was 

 carried out. 



The ground on the Surrey side having been levelled, a wooden 

 curb provided on its exterior with a cast-iron ring, having a cutting 

 edge, was laid upon the levelled ground, and on a framework of short 

 piles to temporarily support it, and ujoon this curb was built, in the 

 form of a tower, the brick lining, that was to be, of the shaft. The 

 outside of the tower was smoothly covered with Roman cement, 

 the material employed in the brickwork itself. As soon as the 

 tower had attained some 20 feet in height, the earth was excavated 

 from within the ring, which then commenced under the weight of the 

 brickwork to cut its way into the earth, and, with the tower, to 

 descend into the excavation. As the tower sank, more and more 

 brickwork was added to the top, and, as need arose, the walls were 

 weighted. In this way the curb was got down to within 40 feet 

 of the required distance, when it stuck fast, and the remainder of the 

 work had to be done by the process of underpinning. The shaft 

 being thus completed down to the required level, and the pumping- 

 machinery having been fixed, an opening was formed in that side of 

 the brick tower which was towards the river, and the driving of the 

 excavation was commenced. This excavation was a perfect rectangle, 

 38 feet wide by 22 feet high, filled with brickwork in Roman cement, 

 but of course leaving the two holes constituting the double roadway. 

 The work was carried out by means of the " Shield." 



Through the kindness of the Council of Trinity College, Dublin, 

 I have been enabled to place on the wall enlarged diagrams of the 

 tunnel. The diagram shows that the shield consisted of twelve 

 vertical frames, placed side-by-side like books upon a book-shelf. 

 Each of these frames extended the full height of the excava- 



