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Marcu 8, 1900. THE MARINE RECORD. ICE-BREAKING STEAMERS. FROM NOTES ON NAVAL PROGRESS. luring the spring of 1899 the ice-breaking steamer Er- mack, by her wonderful work in conveying into Russian _ ports on the Baltic a large number of ice-bound vessels, sug- gested the possibilities of this class of craft asa factor in naval affairs. Although the pioneer ship Britannia, of the Harbor in 1844, lays strong claim to the honor of being the first ice-breaker driven by steam, the first steam vessel especially built for this purpose appears to have been the Pilot, belonging to the port of Cronstadt. She was a small, . single-screw tug, having very sharp lines and great rise of floor, and fitted with a bow fashioned in such a way that the vessel could be forced up on the ice, breaking it down by her weight. The Hamburg authorities soon built similar vessels for the Elbe, such as the Hisbrecker I, of 600 I. H. P., in 1871, and the Scandinavian countries followed with ice-breakers and ice-breaking ferry steamers, propelled by paddles and by single or double screws. The Sleipner, at Copenhagen, of 1,400 tons and 2,600 I. H. P., had the forefoot cut away from a point on the stem above the water line in a slanting direc- __ tion, and striking the keel about one-fourth the vessel’s length from the bow, thus naturally facilitating the mount- ing of the vessel onto the ice field. The discovery was made in America that by going astern vith single screw steamers the disturbance of the water by 3 the propeller had a disruptiag influence of an important _ character, Consequently the St. Ignace, 1,200 tons, built in 1888, and the St. Marie, built in 1893, for service on the Great Lakes, were each provided with a bow propeller. The Sampo, built for the Finnish government, of 2,000 tons and 3,000 I. H. P., has one propeller aft and another forward, and her chief dimensions are: Length, 202 feet; beam, 43 , feet; depth, 29 feet 5 inches. Her contour is such as to strike the ice at a very acute angle, so that when the vessel - is driven with considerable force she has a tendency to rise on the ice in a slanting position, which, while it conduces to bringing her maximum weight to bear, does so in a man- ner which mitigates the blow to the vessel herself. Near the town of Saratoff, on the river Volga, a ferry steamer with four lines of rails for railway cars, not only contends with ice but with varying heights of water; she is assisted, moreover, by an ice-breaker of the ordinary type. There is now also under construction on the shores of Lake Baikal a vessel of 4,200 tons, 290 feet long, 57 feet beam and 7h 28 feet 6 inches deep to the rail deck, designed to ferry 1h: _ Siberian railway cars a distance of 4o miles. The Minto, 1.1 ice-breaking steamer, built by Messrs. Gourlay Bros. & Ca,, Dundee, for the Canadian government’s winter mail aud passenger service between Prince Edward Island and tl» mainland of Canada, has recently (August, 1899) made her trial trip on the Tay, attaining a speed of 16.25 knots. She is 225 feet long, 32 feet 6 inches beam and 20 feet 6 inches molded depth, fitted with water ballast in cellular double bottom and in large, deep tank to ’tween deck aft, for giv- ing her the proper ice-breaking trim. Fully three times as powerful as any vessel previously _ Cunard line, on account of an experience with ice in Boston ® constructed, the Ermack, designed by Vice-Admiral Maka- roff, of the Russian imperial navy, and built last year in England by Messrs. W. G. Armstrong, Whitworth & Co. for the Russian government, deserves particular study, by reason of the novel features in her construction. Her prin- cipal dimensions are as follows: Length, 305 feet; beam, 71 feet; depth to upper deck, 42 feet 6 inches. At no point are the lines of her hull straight, thus assisting in disengaging her from fields of ice when there is danger of her being frozen in. This form of hull and the great strength of the structure would resnit in the ship being lifted bodily rather than giving way, in case the ice closed about it. The strength and rigidity of the hull are so great, in fact, that if the ship should be suspended by the bow and stern without any intermediate support no damage could ensue. The heavy web framing and the plaiting of the ice belt, extend- ing entirely around the hull, like the armor of a modern warship, with a maximum thickness of of 1% inches, render the outer skin impregnable to attacks of ice. The Ermack, like her early precursor, the Pilot, has her STEAM YACHT (SENTINEL.’’ bow designed with a very long overhang, so that the attack on the ice takes the form of a sliding blow, and if the resist- ance encountered is more than sufficient to overcome the breaking strain thus produced, the momentum of the vessel is expended in lifting the bow on tothe top of the ice; meanwhile the water supporting the ice is violently disturb- ed by the action of a propeller arranged under the cutaway bow, so that under the effect of the weight of the vessel act- ing above and enhanced by absence of support below the ice gradually yields. The action thus described will take place continuously when working in thickice. The foremost part of the bow is composed of a solid steel casting. Three screws are placed at the stern, one being on the center line as in ordinary single-screw vessels and the other two as in the usual twin-screw arrangement. The four screws are arranged so that large blocks of ice may be carried clear of the hull or out of the way of the advance of the vessel by means of the current or race due to their working. It is hardly necessary to say that an ice-breaking steamer, to be effective, must have remarkable manceuvring powers, as vessels working in frozen seas have the very smallest space to turn in at times. For this reason the twin-screw arrangement was desirable, but with twin screws the efficiency of the rudder may be lessened, as the propeller race is not thrown directly upon it, as is the case with one screw working directly forward of the rudder. The bow screw is not introduced for speed pur- _ poses, but simply to enable the ship to clear her way and — keep lumps of ice from accumulating under her bottom. All _ four propellers are four-bladed, made of nickel steel, and enormously thick, being calculated to be brought up by ice : without breaking when running at full speed. The machin- ery is all designed to withstand this test. The vessel is divided into 48 absolutely water-tight com- partments, of which 14 are in the double bottom. There is one cross bunker for coal, as well as side bunkers. Thefore _ and after peaks are arranged for trimming purposes, so asto — bring the vessel by the head or stern with water ballast. There are also two heeling tanks amidships. In case the ice crowds the ship on one side, the tank on that side can be filled and an extra pressure of some hundreds of tons brought to bear on it so as to right the ship and crush the ice down © into the water. Both tanks would be filled if it were found that the ice was raising the ship bodily. The weight and ‘ shape of the Ermack would make her roll considerably in a_ sea way, and she cannot have bilge keels, since they would afford a grip hold for the ice; therefore she has also been provided amidships with a third or antirolling tank. Con-— nected with these tanks are pumps of enormous power, so that if the vessel gets caught in the ice her horizontal plane ~ may be varied in any sense desired, whereby she can the more readily release herself. The pump room is a well per- fectly water-tight, let into the middle of the vessel and — descending to within 7 feet of the bottom. The salvage pump has a capacity of 10 tons per minute, and if the ship were flooded above the level of this pump, the latter would be still accessible. The ballast pump is arranged so that it can take hot water from the boilers and pump it into the fore peak, the hot water overflowing through valves in the bow and running down the outside of the skin plating. This is designed with the purpose of preventing rough ice from adhering to the hull. At the stern the vessel is shaped much like a cruiser, but instead of being rounded off hasa deep groove, furnished with fenders, intended to receive the stem of another steamer of the ordinary type in conducting her safely through the broken ice. By means of a powerful winch the second steamer may be braced up taut, and thus be enabled to add her power to that of the ice breaker in struggling with the ice. Another interesting feature is the so-called ice box, an open tube amidships from the main deck down to the water under the ship’s bottom. Through this the boilers are fed with water direct from the sea beneath. This tube is con- nected with a glass pipe set against a wooden scale on which are marked on one side the number of feet that the vessel is CONTINUED ON PAGE 12.