10,000 tons of iron plates were used in the construction of the hull, or 30,000 plates (with about 100 rivets to each), each plate weighing on an average a third of a ton.
The deck, and its strength.
The deck of the ship is double or cellular, and is formed of two half-inch plates, at the bottom, and of two half-inch plates at the top, between which are webs of iron which run the whole length of the ship. The upper deck runs flush and clear from stem to stern for a breadth of about 20 feet on either side of the skylights and hatchways, thereby affording two magnificent promenades for the passengers just within the bulwarks; these promenades are altogether more than the eighth of a mile in length, as four turns up and down either side of them exceed a mile by 640 feet. Between the two side promenades of the upper deck are several quadrangular openings edged with low bulwarks, and looking down into the recesses of the structure. These openings are 42 feet wide, and nearly 60 feet long, the longest being 100 feet, and there are deck gangways connecting the side promenades between each of them. In these spaces the skylights of the large passenger saloons are fixed.
Enormous steam-power from combination of paddle and screw.
The distinguishing feature of the Great Eastern, in addition to her vast size, is the combined application of both the paddle-wheel and the screw. The engines are considerably larger than any previously made for marine purposes. There are ten boilers and five funnels, and each boiler can be cut off from its neighbour and used or not, as desired. The boilers are placed longitudinally along the centre of the ship, and are entirely independent of each other. Every paddle boiler has ten furnaces, and each screw boiler twelve furnaces, thus giving to the whole, the prodigious number of 112 furnaces. The funnels are each about 100 feet in length measuring from the floor of the boilers to the top of the funnel.
The paddle-wheel engines, of which the following is a transverse section, are a magnificent piece of workmanship, combining vast strength with great beauty and apparent lightness of design.
When these, combined with the screw engines (to which reference will presently be made), are at work the mind is lost in wonder at the amount of mechanical power which is thus brought to play in the propulsion of one vessel, and the smoothness and harmony with which that duty is performed, in a space necessarily confined and limited, and amid the violent turmoil of the ocean. No work of art ever yet produced furnishes more exalted ideas of man’s genius and skill than the unceasing and regular motion of these gigantic engines, especially, when we consider the tremendous shocks to which they must be at times subjected, and the delicate nature of some portion of the machinery, resting as this does, not upon solid granite as is the case with land engines, but on the ever straining ribs of a ship.
Paddle-wheel,
The paddle-wheel engines have a nominal power of 1000 horses, they have four cylinders, the diameter of each being 74 inches, with a stroke 14 feet in length, giving 14 strokes per minute. Each cylinder with piston and piston-rod weighs no less than 38 tons, while each pair of cylinders with its crank, condenser, and air-pumps, forms in itself a complete and separate engine, and each of the four cylinders is so constructed that it can be, at once, disconnected when required, from the other three, so that the whole forms a combination of four engines, altogether complete in themselves, whether worked together or separately. The two cranks are connected by a friction-clutch by means of which the two pairs of engines can be connected or disconnected, by a single movement of the hand and at a moment’s warning. All the engines are provided with expansion valves, and their combined force, when working 11 strokes per minute, indicates 3000 horse-power, with steam in the boilers at 15 lbs. on the inch and the expansion valve cutting off at one-third of the stroke. But as all the parts of the engines are so formed and proportioned that they will work safely and smoothly at 8 strokes per minute, with the steam at 25 lbs. and fully open without expansion (beyond what is unavoidably effected by the slides), or at 16 strokes per minute, with the steam in the boiler at 25 lbs. and the expansion valve cutting off at one-fourth of the stroke, they can be made to give a power of 5000 horses. The paddle-shafts are each 38 feet long and weigh 30 tons, while the intermediate cranked shaft, 21½ feet in length, weighs 31 tons.