It is proposed that she should be 800 feet in length with 40 feet beam, and, having a flat bottom, it is calculated that she will not draw more than 11 feet of water with her cargo, passengers, and 500 tons of coal on board—the quantity estimated to be sufficient to take her from Liverpool to New York. The midship part of the ship, of which the following is a transverse section, will, Messrs. Perkins state, be “400 feet in length, or about equal to that of a first-class Atlantic steamer of the present day; she is to have every modern convenience” to accommodate “1000 first-class passengers.” “This vessel,” the projectors add, “is to be fitted with four separate and distinct engines, working independent screws, two of which will be at either end of the boat; they are to be of the collective working power of 12,500 horses, calculated to make the passage either way in 100 hours;” at the average rate of 30 knots an hour.[460]
Considering the great resistance which the displaced fluids must offer to a speed on the ocean so enormous, it is not easy, with our present state of knowledge, to conceive its realization; but the projectors are sanguine of success, and, therefore, while recording the results of the past, I place before my readers such information as is likely to be interesting, or may prove useful for the future. History is of little value, unless it teaches lessons to those who are to fill our vacant places, and, even at the risk of wearying my readers, I have for this reason gone more into detail than I should otherwise have done on such subjects, with a full conviction, that we have still very much more to learn, and especially as regards ships, than one man can hope to teach.
The Engine of the Comet.
Though the different stages of improvement on the steam-ship have been carefully and fully recorded, it may be interesting to notice briefly the progress which has been made in the marine steam-engine itself. With that object I present my readers with a woodcut of the engine of the Comet constructed by James Watt and fitted into that boat by Mr. Robertson, who is still living, and whose photograph accompanies the illustration. This famous machine is now exhibited at South Kensington, in the Museum of Patents.
“COMET” ENGINE.
This engine, which was a “high pressure” one, is simple in construction and light in weight, and, though many improvements have been made since it first drove the Comet, to the wonder of the people on the Clyde, few of these changes have embodied any important principles. Although great strides have been made in the economy of fuel, and in the harmonious working of engines, the general principle of their action has undergone no change. By the reciprocating movements of a steam impelled piston within a closed cylinder, the motive power of the modern steam-ship is obtained, as in the Comet; yet, probably, on no other subject has more mechanical ingenuity been lavished than on the marine engine. Twenty years ago, almost every engineer had his own peculiar type, comprising the “side lever,” the “steeple engine,” the “grasshopper,” the “trunk,” the “oscillating,” and the “direct acting engine,” with an endless variety of sub-combinations; but, after all, these were only variations in the engine left to us by Watt, which, a few years ago, might be seen in some of the small coasting craft plying between the Mersey and the Dee and elsewhere.[461]
Modifications in the construction of Marine Engines.