shaft and crank-pin bearings is 13 inches; the aggregate length of the former bearings is 7 feet 6 inches, and that of each crank-pin 13 inches. The diameter of the propeller-shaft is 12 inches, and the section which passes through the tube is 13 inches in diameter. The screw-propeller is 15 feet in diameter. The boilers are cylindrical, with horizontal tubes, and the pressure of steam 60 pounds per square inch. The indicated horse-power on the measured mile is to be 2,100, and the maximum speed with this power is to be 113 knots. The armament consists of fourteen 64-pounder rifled guns, one of which is a bow-chaser, working under cover of a forecastle, and another is a stern-chaser, under a poop; the remainder of the guns are uncov ered. Sloops of modern date are also of composite build; they are rated next after corvettes, and may be divided into three classes. Those of the first class consist of the Wild Swan and Penguin, completed in 1876, and the Cormorant, Osprey, and Pelican, to be completed this year. These vessels have a displacement of 1,124 tons. The length between perpendiculars is 170 feet, the breadth extreme is 36 feet, and the draught of water forward is 13 feet, and aft, 16 feet. They carry four guns on the broadside and two bow or stern chasers. The estimated cost of the hull, &c., is $169,891, and of the machinery $50,787, in gold. The second class are all completed and in commission, and consist of the Daring, Albatross, Flying Fish, Egeria, Fantôme, and Sappho. These have a displacement of 894 tons; the length between perpendiculars is 160 feet; breadth, extreme, 31 feet 4 inches; draught of water forward, 12 feet; aft, 14 feet; the average indicated horse-power being 900 and the number of guns four, two of which are chasers. Total cost of hull and machinery, $171,558 in gold. The third class, rated by parliamentary returns as sloops and in the navy-list as gun-vessels, consist of the Arab and Lily in commission, each of 700 tons displacement, with the length of 150 feet; breadth, 281 feet, and draught of water forward 10 feet, and aft, 12 feet; the indicated horse-power being respectively 656 and 829. Also of the Flamingo, Condor, Griffon, and Falcon, building and to be completed this year. These last named have a displacement of 774 tons; length, 150 feet; breadth, 29 feet; draught forward, 11 feet; aft, 13 feet; and the indicated horse-power is to be 750. Total cost of hull and machinery, $160,380 in gold. All of these vessels, as well as all other classes of recent construction, are engined on the compound system. The largest of these sloops, i. e., those having a displacement of 1,124 tons, are fitted with engines capable of developing an indicated horse-power of 900 on the measured-mile trials. The diameter of the high-pressure cylinder is 38 inches, of the low-pressure cylinder 66 inches, and the stroke of piston 2 feet. The maximum revolutions are to be 100 per minute, and the speed under steam in smooth water between 9 and 10 knots per hour. The steam is supplied by cylindrical boilers, and the pressure is to be 60 pounds per square inch. The screw-propeller is 13 feet in diameter, and like those of other cruising vessels it is two-bladed and lifting. The vessels are to be fully rigged as cruisers, and intended to keep the sea under sails. The Arab class are also three-masted; they are square-rigged on the main-mast as well as on the fore-mast. There are also a large number of what is known as composite gunvessels fitted as cruisers, of which the Coquette class are the smallest sea-going vessels in the British navy. The displacement of this class is 430 tons; the length is 125 feet; breadth, extreme, 23 feet 6 inches; S. Ex. 27- -8 draught forward, 8 feet; aft, 10 feet. They also have lifting-screws, are three-masted, and square-rigged on the fore-mast only. The armament consists of two 64 and two 20-pounder rifles. The speed under steam is only about 8 knots in smooth water at the best, but under favorable conditions of wind and weather a run of twenty-four hours can be made with 3 tons of coal. In addition to the composite gunvessels and gunboats, there is a large number of iron double-screw gunboats, ten of which were building by the Palmer Ship-building Company at Jarrow-on-Tyne, at the time of my visit to that place last summer. These vessels have a dis placement of 363 tons; the indicated horse-power is to be 310, and the number of guns three. Quite a number are of still smaller size, and some of them are fitted to carry a single gun mounted on a rising and lowering platform forward, so arranged that the gun can be lowered into the hold when the vessel goes to sea. This peculiar type of vessel was invented by Mr. Rendel; the Staunch, built in 1867, being the original. She cost $64,481 in gold. Since then about thirty have been added to the navy. Recently, Sir W. Armstrong & Co. have been constructing four gun boats for the Chinese government, in which several important improve ments over the Staunch type have been introduced. Two of these boats, each mounting a 26-ton gun, have already been delivered at Tientsin, and two others, each mounting a 38-ton gun, are probably by this time completed and ready to sail for China. These two last little vessels, built of iron, measure 126 feet over all, their extreme breadth is 30 feet, draught of water 8 feet, and displacement 430 tons. They are schooner-rigged, with tripod-masts, carry 50 tons of coal, 50 rounds of ammunition, and, in addition to the heavy gun, they carry two 12-pounders and a Gatling gun. They are propelled by twin-screws, and are intended to have a speed of 9 knots. The main peculiarities consist in the great gun mounted on so small a vessel, and the system of working it; the piece being much heavier than those used in the English boats, and the little vessel is herself made to act as the gun carriage. The gun is worked by hydraulic power, and the entire arrangement of the mechanism is similar to that employed in working the 100-ton gun at Spezia, to be noticed hereafter. Two heavy iron beams in the fore part of the vessel are placed side by side on a level with the deck and parallel with the keel; on these beams are bolted frames analogous to the cross-head guides of a horizontal engine, and the trunnions of the gun are fitted in slide-blocks, these last taking the place of the cross-head. Thus arranged, the gun can slide back and forth through a range of about 3 feet. The preponderance at the breech-end is supported by two secondary parallel bars inside the main gun-beams. These are hinged at the rear end, while at the forward end they are carried on the cross-head of a vertical hydraulic ram fixed beneath the deck. The breech-end of the gun is supplied with a hoop and lugs; the lugs rest on the two secondary bars near their hinged ends, and thus, by causing the hydraulic ram to rise or fall, the gun can be elevated or depressed at will. No turning-gear is provided, the lat eral training of the gun being effected by turning the whole boat through the required arc by the use of the rudder and twin-screws. To run the gun in and out, two hydraulic cylinders are used, one of which is fixed horizontally on each side-beam, the cross-heads of the rams taking hold of the trunnion slide-blocks. The recoil is taken up by these rams, or more properly pistons, delivering water under a weighted valve. The gun is loaded by a hydraulic rammer, the shot being brought to the muzzle by a trolley or carriage, off which it is pushed into the bore. During the trials of the Gamma, one of the vessels just tested, the 38-ton gun was fired with charges consisting of 130 pounds of powder behind an 800-pound projectile, the elevation being 3 degrees. These boats are regarded as the nucleus of a Chinese hornet fleet, which fleet, if properly manned, will no doubt give a deal of trouble to Japan or any other country which may dare to invade the sanctity of Celestial waters. Extravagant estimates of their merits have, however, been formed, and some of the English papers have been urging the adoption of the type into the British navy. They are a great improvement on the English boats, but not free from objections, one of which is the want of lateral movement of the gun without moving the vessel, and in order that they may operate with maximum efficiency the water must be tolerably smooth; and at such a time it would not be difficult to hit one of them by a shot from the small rifled guns carried by armored ships and send her to the bottom. Therefore, except under peculiar circumstances, they are useful for defensive purposes only, and service on board of them must in many cases during war be attended with extreme risk. COMPOSITE SYSTEM. All the modern cruising vessels of the British navy (unarmored) below the rate of the Active are now built on the composite system. In this method of construction the frame-work inside of the skin, including frames, beams, keelsons, stringers, shelf-pieces, water-ways, transoms, bulkheads, &c., are of iron, and arranged nearly as they would be in an ordinary iron-built ship, the frames and beams being of the same kind and dimensions and spaced the same distances apart, with bulkheads of the usual number and construction. The keel, stem, outside planking, and decks are of wood. The planks are put on in two courses laid fore and aft. The first course is secured to the iron frames by g-inch Muntz'smetal bolts tapped into the iron, having also lock-nuts on the points inside. The bolts have screw-driver heads, and are screwed home against a shoulder so as to leave the head below the surface of the plank, the cavity over the head of the bolt being filled with white and red lead so as to prevent leakage. The planks on both sides, as well as the iron, are carefully painted; after the first course of planks have been carefully calked between the joints with oakum, the second course is laid on it, breaking joints with the planks of the first course. The planks of this second course are fastened to those of the first course by copper bolts driven through both thicknesses, and riveted inside the vessel. The joints between the planks of the last course are then likewise calked, and the surface below water coppered over. The kind of wood used is teak; the thickness of the first course of planks is about 31⁄2 inches, and of the second course about 3 inches; the width is about 12 inches, and there are two bolts to every frame through each plank of the first course. The work is required to be carefully done, and special attention is directed to see that the iron is completely insulated or cut off from electrical communication with the copper sheathing and bolts used in the structure. In this system of ship-construction the same strength of hull is not expected to be attained as when the hull is composed entirely of iron, having each skin-plate riveted to the next, also to the frames and the bottom, and decks tied together by bulkheads; the constructors employed in building them, however, estimate the strength of one of these well-built composite vessels to be from 40 to 50 per cent. greater than the strength of a wood-built vessel of the same dimensions, besides which the durability is infinitely greater, for there is no wear-out of the interior parts, and the skins are of teak, which possesses durability equal to our live-oak. |