20 ANNUAL OF scip:ntific discovery. 



driven beneiitli the bed of the sea; by submerged roadways and 

 tubes; by hirge terr3'-boats carrying trains on board; and by 

 bridges to be carried on piers formed on islands to be sunk in the 

 Straits. A ferrv-boat, lar^^e enouirh to receive a whole ordinarv 

 train on boaril, would be a material improvement on the present 

 means of conveyance. Such boats cannot, however, be em- 

 ployed, except by the construction of special harbors on each 

 coast. With reference to a tunnel, it has \)cc\\ proposed to drive 

 one of onlinary size for a double liui; of railway, which shall de- 

 scend by a gradient of one in GO on each side of the channel to a 

 depth of about 270 feet below the bed of the sea. Tiie total 

 length of the tunnel would be 30 miles, of which 22 would be 

 beneath the sea. A special commission, api)()inted by the Em- 

 peror of the Fnuich, recently reported in favor of a submarine 

 tunnel. We propose to lay a tube of cast iron on tiie bottom of 

 the sea, between coast and coast, to be commenced on one side 

 of the channel, and to be built up within the inside of a horizon- 

 tal cylinder, or bell, or chamber, which shall be constanLl}- pushed 

 forward as the building up of the tube proceeds. The bell or 

 chamber within which the tube is to be constructed will be about 

 80 feet in length, 18 feet internal diameter, and composed of cast- 

 iron rings 8 inches thick, securely bolted together. The interior 

 of the bell will be bored out to a true cylindrical surface, like the 

 inside of a steam cylinder. The tube to be constructed within it 

 will consist of cast-iron i)lates, in segments 4 inches in thickness, 

 connected by llanges, boiled together inside the tube, leaving a 

 clear diamciter of 13 feet. Surrounding this tube, and forming 

 part of it, will be constructed annular discs or diaphragms, the 

 outside circumference of which will accurately fit the interior of 

 the bell. These diaphragms will be furnished with arrangements 

 for making perfectly water-tight joints, for the purpose of ex- 

 cluding sea-water and securing a dry chamber, within which the 

 various operations for building up the tul)e, and for pressing for- 

 ward the bell as each ring of the tube is added, will be performed. 

 Tliere will alwavs be 3 and generallv 4 of these watcr-ti<i:ht 

 jomts contained within the bell. A clear space between the end 

 of the tube and the end or projecting part of the bell of 3C feet 

 will be left as a chamber lor the various operations. Within this 

 chamber, powerful hydraulic presses, using the built and com- 

 pleted portion of the tube as a fulcrum, will, as each ring is com- 

 pleted, push forward the bell to a suiBeient distance to admit the 

 addition of another ring to the tube. The bell will slide over the 

 water-tight joints described, one of which will be left behind as 

 the bell is projected forward, leaving 3 always in operation 

 against the sea. The weight of the bell and of the machinery 

 within it will be a little in excess of the weight of water dis- 

 placed, and therefore the only resistance to be overcome by the 

 hydraulic presses when pushing forward the bell is the friction 

 due to the slight difl'erence in weight and the head or column of 

 water pressing upon the sectional are^ of the bell against its for- 

 ward motion. In like manner, the specin(! gravity of the tube 

 will be a little in excess of the weiy:ht of water which it dis- 



