Discoveries and Inventions of the Nineteenth Century

was 100 ft. long, 36 ft. wide, and 13 ft. high. Each of her ten boilers weighs 50 tons, and when all are in action, 12 tons of coal are burnt every hour, and the total displacement of the vessel laden with coal is 22,500 tons. 1. She was broken up for old iron, 1889. Fig. 63.—The Great Eastern ready for Launching. The use of steam power in navigation has increased at an amazing rate. Between 1850 and 1860 the tonnage of the steam shipping entering the port of London increased three-fold, and every reader knows that there are many fleets of fine steamers plying to ports of the United Kingdom. There are, for example, the splendid Atlantic steamers, some of which almost daily enter or leave Liverpool, and the well-appointed ships belonging to the Peninsular and Oriental Company. The steamers on the Holyhead and Kingston line may be taken as good examples of first-class passenger ships. These are paddle-wheel boats, and are constructed entirely of iron, with the exception of the deck and cabin fittings. Taking one of these as a type of the rest, we may note the following particulars: the vessel is 334 ft. long, the diameter of the paddle-wheels is 31 ft., and each has fourteen floats, which are 12 ft. long and 4 ft. 4 in. wide. The cylinders of the engines are 8 ft. 2 in. in diameter, and 6 ft. 6 in. long. The ship cost 137about £75,000. The average passage between the two ports—a distance of 65½ miles—occupies 3 hours 52 minutes, and at the measured mile the vessel attained the speed of 20·811 miles per hour. As an example of the magnificent vessels owned by the Cunard Company, we shall give now a few figures relating to one of their largest steam-ships, the Persia, launched in 1858, and built by Mr. N. Napier, of Glasgow, for the company, to carry mails and passengers between Liverpool and New York. Her length is 389 ft., and her breadth 45 ft. She is a paddle-wheel steamer, with engines of 850 horse-power, having cylinders 100 in. in diameter with a stroke of 10 ft. The paddle-wheels are 38 ft. 6 in. in diameter, and each has twenty-eight floats, 10 ft. 8 in. long and 2 ft. wide. The Persia carries 1,200 tons of coal, and displaces about 5,400 tons of water. Fig. 64.—Comparative Sizes of Steamships.1838, Great Western; 1844, Great Britain; 1856, Persia; 1858, Great Eastern.A, Section amidships of Great Eastern; B, The same of Great Western. Both on the same scale, but on a larger one than their profiles. A velocity of twenty-six miles per hour appears to be about the highest yet attained by a steamer.[2] This is probably near the limit beyond which the speed cannot be increased to any useful purpose. The resistance offered by water to a vessel moving through it increases more rapidly than the velocity. Thus, if a vessel were made to move through the water by being pulled with a rope, there would be a certain strain upon the rope when the vessel was dragged, say, at the rate of five miles an hour. If we desired the vessel to move at double the speed, the strain on the rope must be increased four-fold. To increase the velocity to fifteen miles per hour, we should have to pull the vessel with nine times the original force. This is expressed by saying that the resistance varies as the square of the velocity. Hence, to double the speed, the impelling force must be quadrupled, and as that force is exerted through twice the distance in the same time, an engine would be required of eight times the power—or, in other words, the power 138of the engine must be increased in proportion to the cube of the velocity; so that to propel a boat at the rate of 15 miles an hour would require engines twenty-seven times more powerful than those which would suffice to propel it at the rate of five miles an hour. 2. This has now (1895) been far surpassed.—Vide infra. The actual speed attained by steam-ships with engines of a given power and a given section amidships will depend greatly upon the shape of the vessel. When the bow is sharp, the water displaced is more gradually and slowly moved aside, and therefore does not offer nearly so much resistance as in the opposite case; but the greater part of the power required to urge the vessel forward is employed in overcoming a resistance which in some degree resembles friction between the bottom of the vessel and the water. The wonderful progress which has, in a comparatively short time, taken place in the power and size of steam-vessels, cannot be better brought home to the reader than by a glance at Fig. 64, which gives the profiles of four steamships, drawn on one and the same scale, thus showing the relative lengths and depths of those vessels, each of which was the largest ship afloat at the date which is marked below it, and the whole period includes only the brief space of twenty years!—for this, surely, is a brief space in the history of such an art as navigation. All these ships have been named in the course of this article, but in the following table a few particulars concerning each are brought together for the sake of comparing the figures: Date. Name. Propulsion. Length. Breadth. 1838 Great Western Paddles 236 ft. 36 ft. 1844 Great Britain Screw 322 ft. 51 ft. 1856 Persia Paddles 390 ft. 45 ft. 1858 Great Eastern Screw and paddles 690 ft. 83 ft. Fig. 65.—The s.s. City of Rome. Several passenger ocean-going steamships have been built since the Persia, of still greater dimensions, and of higher engine power. These 139have generally been surpassed in late years by some splendid Atlantic liners, such as the sister vessels owned by the International Navigation Co., and now named respectively the New York and the Paris. The City of Rome, launched in 1881 by the Barrow Steamship Co., is little inferior in length to the Great Eastern, although the tonnage is only about one-third. The City of Rome is 560 ft. long, 52 ft. wide, and 37 ft. deep. Her engines are capable of working up to 10,000 indicated horse-power. Fig. 65 is a sketch of this ship, and shows that she carries four masts and three funnels. The main shaft measures more than 2 ft. across, and the screw-propeller is 24 ft. in diameter. She has accommodation for 1,500 passengers, and is fitted with all the conveniences and luxuries of a well-appointed hotel. The International Navigation Co.’s ship Paris, has made the passage across the Atlantic in less than six days, and appears to be the fastest vessel in the transatlantic service. In August, 1889, she made the run from shore to shore in 5 days, 22 hours, 38 minutes. The extraordinary increase in the speed of steamships that has been effected within the last few years depends mainly upon the improvements that have latterly been made in the marine engine—a machine of which we have been unable to give an account, because its details are too numerous and complicated to be followed out by the general reader. Suffice it to say, that the use of higher steam pressures with compound expansion (p. 18), condensers which admit of the same fresh water being used in the boilers over and over again, and better furnace arrangements, are among the more important of these improvements. But not only have the limits of practicable speed been enlarged, but a greater economy of fuel for the work done has been attained; the result being that ocean carriage is now cheaper than ever. The outcome of this will not cease with simply a greatly extended steam navigation, but appears destined ultimately to produce effects on the world at large comparable in range and magnitude with those that may be traced to the use of the steam engine itself since its first invention. Among the curiosities of steamboat construction may be mentioned a remarkable ship which was built a few years ago for carrying passengers across the English Channel without the unpleasant rolling experienced in the ordinary steamboats. The vessel, which received the name of the Castalia, was designed by Captain Dicey, who formerly held an official position at the Port of Calcutta. His Indian experience furnished him with the first suggestion of the new ship in the device which is adopted there for steadying boats in the heavy surf. The plan is to attach a log of timber to the ends of two outriggers, which project some distance from the side of the vessel; or sometimes two canoes, a certain distance apart, are connected together. Some of these Indian boats will ride steadily in a swell that will cause large steamers to roll heavily. Improving on this hint, Captain Dicey built a vessel with two hulls, each of which acted as an outrigger to the other. Or, perhaps, the Castalia may be described as a flat-bottomed vessel with the middle part of the bottom raised out of the water throughout the entire length, so that the section amidships had a form like this— The two hulls were connected by what we may term “girders,” which extended completely across their sections, forming transverse partitions or bulkheads, and these girders were strongly framed together, so as to form rigid triangles. These united the two hulls so completely, that 140there was not any danger of the vessel being strained in a sea-way. The decks were also formed of iron, although covered with wood, so that the whole vessel really formed a box girder of enormous section. Fig. 66.—The Castalia in Dover Harbour. The reason why the steamers which until lately ran between Dover and Calais, Folkestone and Boulogne, and other Channel ports, were so small, was because the harbours on either side could not receive vessels with such a draught as the fine steamers, for example, which run on the Holyhead and Kingston line. Now, the Castalia drew only 6 ft. of water, or 1 ft. 6 in. less than the small Channel steamers, and would, therefore, be able to enter the French ports at all states of the tide. Yet the extent of the deck space was equalled in few passenger ships afloat, except the Great Eastern and some of the Atlantic steamers. The vessel was 290 ft. in length, with an extreme breadth of 60 ft. The four spacious and elegantly-fitted saloons—two of which were 60 ft. by 36 ft., and two 28 ft. by 26 ft.—and the roomy cabins, retiring rooms, and lavatories, were the greatest possible contrast to the “cribbed, cabined, and confined” accommodation of the ordinary Channel steamers. There were also a kitchen and all requisites for supplying dinners, luncheons, etc., on board. But besides the above-named saloons and cabins, there was a grand saloon, which was 160 ft. long and 60 ft. wide; and the roof of this formed a magnificent promenade 14 ft. above the level of the sea. There was comfortable accommodation in the vessel for more than 1,000 passengers. The inner sides of the hulls were not curved like the outside, but were straight, with a space between them of 35 ft. wide, and the hulls were each 20 ft. in breadth, and somewhat more in depth. There were two paddle-wheels, 141placed abreast of each other in the water-way between the two hulls, and each of these contained boilers and powerful engines. The designers of this vessel calculated that she would attain a speed of 14¾ knots per hour, but this result failed to be realized. Probably there were no data for the effect of paddles working in a confined water-space. The position of the paddles is otherwise an advantage, as it leaves the sides of the vessel free and unobstructed. The ship had the same form at each end, so it could move equally well in either direction. There were rudders at both ends, and the steering qualities of the ship were good. Although the speed of the Castalia was below that intended, the vessel was a success as regards steadiness, for the rolling and pitching were very greatly reduced, and the miseries and inconveniences of the Channel passage obviated. Fig. 67.—The Castalia in Dover Harbour—End View. The Castalia is represented in Figs. 66 and 67. She was constructed by the