TRANSACTIONS OF THE SECTIONS. 207 



Avitliiu it will consist of cast-iron plates in segiiients 4 inches in thickness, connected 

 by flanges, bolted tog-ether inside the tube, leaving- a clear diameter of 13 feet when 

 finished. Surrounding- this tube and forming part of it, ^\•ill be constructed annular 

 disks or diaphragms, the outside circumference of which will accui-ately tit the 

 interior of the bell. These diaphragms will be furnished with arrangenients for 

 making- perfectly watertight joints for the piu-pose of excluding sea-water and 

 secm-ing a dry chamber, within which the various operations for building up the 

 tube, and for pressing forward the bell as each ring of the tube is added, will bo 

 performed. There will always be three and generallj- four of these waterti"-ht 

 joints contained within the bell. A clear space between the end of the tube and the 

 end or projecting part of the bell, of 30 feet, will be left as a chamber for the various 

 operations, "\^"ithin this chamber, powerful hydraulic presses, using the built and 

 completed portion of the tube as a fulcrum, will, as each ring is completed, push 

 forward the bell to a sufficient distance to admit the addition of another ring to 

 the tube. The bell will slide over the watertight joints described, one of which 

 will be left behind as the bell is projected forward, leading three always in operation 

 against the sea. The weight of the bell and of the machinerj' within it will be a 

 little in excess of the weight of water displaced, and therefore the only resistance 

 to be overcome by the hydraulic presses when pushing forward the "bell, is the 

 friction due to the slight ditterence in weight and the head or column of water 

 pressing upon the sectional area of the bell against its forward motion. In like 

 juanner, the specific gravity of the tube will be a little in excess of the weight of 

 water which it displaces; and in order to obtain a, lirm footing upon the bottom of 

 the sea, the tube will be weighted by a lining of brick in cement, and for further 

 protection will be tied to the ground by screw piles, which will pass through 

 stuffing boxes in the bottom of the tube. These piles will, during the construction 

 of the tube within the bell-chamber, be introduced in the annular space between 

 the outside of the tube and the inside of the bell, and will be screwed into the 

 ground as they are left behind by the progTession of the bell. The hydraulic 

 presses and the other hydraulic machinery, which will be employed for lifting and 

 fixing the various segments of the tube, will be supplied with tlie power required 

 for working them from accumidators on shore, on Sir William Armstrongs system, 

 and the supply of fresh air required for the sustenance of the workmen employed 

 within the bell and within the tube will be insured also by steam power on shore. 

 As the tube is completed, the rails will be laid within it for the trains of waa-o-ons 

 to be employed in bringing up segments of the rings as they may be required for 

 the construction of the tube, and for taking back the waste water from the hydraulic 

 presses, or any water from leakage during the construction. 



The tube will be formed of rings of 10 feet in leng-th, each ring consisting of six 

 segments, all precisely alike, turned and faced at the flanges or joints, and fitted 

 together on shore pre-Nious to being taken into the bell, so that on their arrival the 

 segments may, with perfect certainty and precision, be attached to each other. 

 Every detail of construction has been designed, and so iar as we can see, no contin- 

 gency has been left unprovided for. The possibility of injury by anchors or wrecks, 

 or submarine currents has also been investigated. The tube" when laid will be 

 secure from aU dangers arising from such causes. 



The building of the tube will be commenced on dry land above the level of the 

 sea, and will be gradually submerged as the tube lengthens. The operations on 

 drj' land will be attended with more difficulty than those underwater; but all these 

 circumstances have been carefully considered and provided for. The rings forming 

 the tube will be made by special machinery, to be expressly constructed for facili- 

 tating the work and economising the cost. This machineiy is all desio-ned and 

 specified. The first half-mile will test the feasibility of construction ; for that will 

 have to be built both above and under water. "When once fairly under water the 

 progress should be rapid, and it is estimated that the whole uiidertakino- may be 

 easily completed in five years from the commencement. 



The precise line to be taken betwixt the English and French coasts can hardly 

 be determined without a more minute survey of the bottom of the Channel than at 

 present exists. It will probably be between a point in close proximity to Dover on 

 the English coast, and a point in close proximity to Cape Grisnez on the French 



