“Well, it has been brilliantly successful.”
“I looked at the animal closely, and found that it was covered with a couple of valvular shells in front; these shells seem to act as a shield, and after many attempts I elaborated the boring-shield which was used in hollowing out the Thames Tunnel.”
This statement, which we can imagine to have been made by Sir Marc Isambard Brunel to a friend, is no doubt in substance quite true. A writer in the “Edinburgh Encyclopædia” says, that Sir M. I. Brunel informed him, “that the idea upon which his new plan of tunnelling is founded, was suggested to him by the operations of the Teredo, a testaceous worm, covered with a cylindrical shell, which eats its way through the hardest wood.”
Two or three attempts had already been made to drive a tunnel under the Thames, but they had ended in failure. In 1823, Brunel came forward with another proposal, and he ultimately succeeded.
This illustrious engineer must not be confounded with his son—who was also a celebrated engineer—Isambard Kingdom Brunel. There were two Brunels, father and son, even as there were two Stephensons, George and Robert.
Sir Marc Isambard Brunel, the father, whose most notable enterprise was the Thames Tunnel, was a French farmer’s son, and after various experiences in France and America settled in England in 1799, and married the daughter of William Kingdom of Plymouth. He had already succeeded as an engineer so well as to be appointed chief engineer of New York, and a scheme for manufacturing block-pulleys by machinery for vessels was accepted by the British Government, who paid him £17,000 for the invention. He was also engaged in the construction of Woolwich Arsenal and Chatham Dockyard, etc., and in 1823 he came forward with another proposal for the Thames Tunnel.
In that same year, his son, Isambard Kingdom Brunel, entered his father’s office, and assisted in the construction of the tunnel. The son subsequently became engineer to the Great Western Railway, and designed the Great Western steamship.
But though Brunel’s proposal for the tunnel was made public in 1823, the work was not actually commenced until March, 1825. It was to cross under the river from Wapping to Rotherhithe, and present two archways. And if you had been down by the Rotherhithe bank of the Thames about the latter date, you would have been surprised to see that instead of hollowing out a shaft, proceedings began by raising a round tower.
A space was traced out, some 50 feet across, and bricklayers began to build a circular hollow tower about 3 feet thick and 42 feet high.
This tower was strengthened by iron bars, etc., and then the excavation commenced within. The soil was dug out and raised by an engine at the top, which also pumped out water. And as the hollow proceeded, the great shaft or tube of masonry sank gradually into it. Bricklayers added to its summit until it reached a total height of 65 feet, which in due course was sunk into the ground.