The Great Eastern steamship was fitted up with three tanks to receive the Cable, one situated in the forehold, one in the afterhold, and the third nearly amidships. The bottoms and the first tier of plates were of five-eighths iron, and each tank, when completed to this height, and tested as to its tightness by filling it with water, and found or made to be perfectly watertight, was let down from its temporary supports on to a bed of Portland cement, three inches in thickness, and the building up and riveting of the remaining tiers was continued. The beams beneath each tank were shored up from the floor beneath it down to the kelson with nine inches Baltic baulk timber, and it will give some idea of the magnitude of the work to state that upwards of 300 loads of this material were required for this purpose alone. The dimensions of the fore tank were 51 ft. 6 in. diameter by 20 ft. 6 in. in depth, and its capacity was for 693 miles of Cable. The middle tank was 58 ft. 6 in. broad, and 20 ft. 6 in. deep, and held 899 miles of Cable, and the after tank was 58 ft. wide and 20 ft. 6 in. deep, and contained 898 miles. The three tanks were therefore capable of containing in all 2,490 miles of the new Cable.
The experience gained on board the Agamemnon and Niagara, and the practical knowledge obtained by the telegraphic engineers, were turned to good account in erecting the new machinery on the deck of the Great Eastern for paying-out the Cable.
Over the hold was a light wrought-iron V wheel, the speed of which was regulated by a friction wheel on the same shaft. This was connected with the paying-out machinery by a wrought-iron trough, in which, at intervals, were smaller wrought-iron V wheels, and at the angles vertical guide wheels. The paying-out machinery consisted of a series of V wheels and jockey or riding wheels (six in number); upon the shafts of the V wheels were friction wheels, with brake straps weighted by levers and running in tanks filled with water: and upon the shafts of the jockey wheels were also friction straps and levers, with weights to hold the Cable and keep it taut round the drum. Immediately before the drum was a small guide wheel, placed under an apparatus called the knife, for keeping the first turn of the Cable on the drum from riding or getting over another turn. The knives, of which there were two, could be removed and adjusted with the greatest ease by slides similar to a slide-rest of an ordinary turning-lathe. One knife only was used, the other being kept ready to replace it if necessary. The drum, round which the Cable passed, was 6 feet diameter and 1 foot broad, and upon the same shaft were fixed two Appold’s brakes, running in tanks filled with water. There was also a duplicate drum and pair of Appold’s brakes fitted in position and ready for use in case of accident. Upon the overhanging ends of the shafts of the drums driving pulleys were fitted, which could be connected by a leather belt for the purpose of bringing into use the duplicate brakes, if the working brakes should be out of order. Between the duplicate drum and the stern wheel were placed the dynamometer and intermediate wheels for indicating the strain upon the Cable. The dynamometer wheel was placed midway between the two intermediate wheels, and the strain was indicated by the rising or falling of the dynamometer wheel on a graduated scale of cwts. attached to the guide rods of the dynamometer slide. The stern wheel, over which the Cable passed when leaving the ship, was a strong V wheel, supported on wrought-iron girders overhanging the stern, and the Cable was protected from injury by the flanges of this wheel by a bell-mouthed cast-iron shield surrounding half its circumference.
Close to the dynamometer was placed an apparatus similar to a double-purchase crab, or winch, fitted with two steering wheels, for lifting the jockey or riding wheels with their weights and the weights on the main brakes of the drum, as indications were shown upon the dynamometer scale.
All the brake wheels ran in tanks supplied with water by pipes from the paddle-box tanks of the ship.
The Cable passed over the wrought-iron V wheel over the tank along the trough, between the V wheels and jockey wheels in a straight line; four turns round the drum where the knife comes into action over the first intermediate wheel, under the dynamometer wheel, and over the other intermediate and stern wheels into the sea.
