Tunnel at Roiherhithe. 73 



present state of this Tunnel, the plan of which was described 

 in the Phil. Mag. vol. lxxii. p. 139. 



Numerous fine drawings and sections were hung up in the 

 lecture-room, and upon the table was a model illustrative of 

 one part of the apparatus now in use ; and also some of the 

 smaller parts of the apparatus itself. The principle and pro- 

 ceedings which have advanced the work to its present state 

 were explained from the table by Mr. Faraday, for Mr. Bru- 

 nei. A tower of brick-work was first erected upon an iron 

 and wooden curb, furnished beneath with a cutting edge ; this 

 tower or cylinder was tied together by forty-eight vertical 

 bolts, half iron and half wood, and by thirty- seven horizontal 

 and imbedded wooden hoops. The tower was forty feet high, 

 fifty feet external diameter, three feet thick, required 250,000 

 bricks, and 1000 barrels of cement, and weighed about 1000 

 tons. The mode of sinking this cylinder was then described, 

 first, by removing the short piles on which it had been built, 

 and then by taking away the earth from the inside ; and the 

 complete command of the tower during its descent explained 

 and illustrated. Being, with the exception of seven feet, sunk 

 into the earth, it was underpinned for twenty-four feet, and 

 then a second smaller cylinder was lowei'ed in the same man- 

 ner, at the bottom of the first, for the purpose of a reservoir. 

 This was described, as also the manner in which this enormous 

 shell of brick-work was completed, and was, and is still, pre- 

 served from injury by the pressure of the surrounding earth 

 and water ; the whole mass weighs about 2000 tons, and, not- 

 withstanding, is buoyant by about 150 tons. The depth from 

 the top to the bottom is about eighty feet. The advantages 

 of this process of sinking the tower consists essentially in dis- 

 pensing with a coffer-dam, and the consequent diminution of 

 expense ; in the comparatively small quantity of ground re- 

 quired on the surface ; and in the utter absence of all interfe- 

 rence with the neighbouring houses : although surrounded by 

 houses on all sides, within twenty-five feet, not the slightest 

 shake or disturbance has been occasioned. 



The horizontal progress was then described, and the pecu- 

 liar frame-work by which Mr. Brunei makes safe progress in 

 any kind of ground illustrated by large sectional drawings. 

 The section of the brick-work is thirty-six feet six inches by 

 twenty-one feet six inches ; and the section of the two- ways, 

 each thirteen feet six inches wide, by sixteen feet high. The 

 work has been carried forward 130 feet, the tunnel being com- 

 pleted immediately up to the frames. The numerous accidents 

 of ground, and the manner in which they were met and ob- 

 viated by the apparatus, were strikingly illustrative of its 



Vol. 68. No. 339. July 1826. K powers, 



