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1899.] MARINE RIEV TE W. 19 rounded form, and to have the outside surfaces as smooth as possible, both seams and butts for this reason being flush plated. It is desirable also that the vessels relatively should be short and broad, as this is found to greatly assist their manetvring in ice, and prevents the broken pieces from clinging to the shell plating. It is also important to have the pumps of enormous power, connected with trimming tanks both at the bow and stern, and also at the sides of the ship, 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. Experience with the Sampo and Ermack has shown that pack ice of practically any thickness can be negotiated; and in the case of the latter vessel, she On one Occasion encountered a pack which was measured and found to be of a total thickness of 34 feet, 9 feet being above the level of the field, and through which she successfully forced her way--a feat which would have been quite impossible but for the action of the forward pro- peller. As regards the propellers themselves, I may mention that we have made them both of bronze and of nickel steel, and have not so far had a broken blade, and this in spite of the fact that on many occasions the engines have brought up "'all standing,' which, I need hardly say, requires their being designed in all their working parts, both as regards scantlings and surfaces, on a basis greatly in excess of what is usual in machinery for ordinary purposes. The Ermack has broken composed ice of 8 feet 3 inches in thickness, and she has gone through field ice of about 40 inches, with 6 inches of snow upon it, at a speed of 2% to 3 knots; moreover, she has been driven at a speed of about 10 knots through clear ice of 24 inches, whilst ice under 18 inches has little effect upon her. It is found that snow has a wonderfully great retarding in- fluence upon an ice-breaker, much more so than a similar thickness of solid ice. Maneuvring powers of the Ermack are remarkable, seeing that with her helm only she can turn in a circle of only twice her own length, and her handiness was specially shown when she entered the frozen-up port of Cronstadt on March 16 last, proceeding without stopping through an entrance only 95 feet wide and berthing herself alongside the quay with- out assistance, whereas under ordinary circumstances of navigation in open water, steamers are in the habit of invariably being assisted by tug boats. Her practical utility was not long in being put to the test. Im- mediately on her arrival urgent word was received from Reval that a number of steamers were in great jeopardy; she at once proceeded there, and was the means of liberating thirty-three steamers of an aggregate ~ value of $7,500,000. She subsequently returned to Cronstadt and St. Petersburg and was instrumental in relieving anid facilitating the entry of some forty more steamers several weeks earlier than if they had waited the ordinary opening of navigation. The above performance is a very con- clusive proof of the commercial value of such a vessel. When a passage has once been broken, vessels of ordinary construction can usually follow in the channel thus made without suffering injury; where, however, vessels are intended to work regularly in this way, it would be advisable to give them a little additional strengthening, especially as regards the bow, and as regards the propeller, this had better be of steel somewhat stronger than ordinary practice. It is necessary here to point out that all the foregoing remarks apply to ice-breaking in the Baltic, or where the ice is formed gradually at moderate temperatures, and that the same result could not be looked for in the case of service in the Arctic regions where the ice is of a much harder and more brittle description, and it probably would not be prudent to have the bow propeller shipped when a vessel is employed among the heavy ice of the Polar seas. In connection with the Ermack I must not fail to mention the name of Vice-Admiral Makaroff, of the imperial Russian navy, but for whose personal initiative this important vessel would never have been built, and from whom we received very much valuable assistance during the vessel's construction. x very important application of ice-breaking steamers is shown in their ability to form connecting links in railway systems in crossing large stretches of water--which it would be either impossible or too costly to bridge--and of which we ourselves have had two notable examples. Near the town of Saratoff on the river Volga, there is an important railway traffic, which during the winter was practically suspended and could only be carried on in a desultory way when the ice was strong enough to bear sledge traffic; but there were occasions both in the spring and autumn when communication, either by sledge or navigation, was absolutely im- Possible. In this case there was a further difficulty in the large range in the depth of water; it sometimes was as low as 10 feet; but with the melt- Ing snows in spring the water rose to the extent of 45 feet. It became necessary to design a vessel which could not only contend with the ice, but load and discharge the railway wagons at varying heights. We therefore proposed a twin-screw vessel oi the following dimensions: Length, 252 feet; breadth, 55 feet 6 inches; depth, 14 feet 6 inches. This vessel has four lines of rails, each pair converging into two hydraulic lifts placed side by side at the bow of the vessel, and it is found in prac- tice that the full load of twenty-four cars.can be run off or on to the shore in half an hour. and this at varying heights according to the depth of the water. Owing to the limited draught of the water it was not Possible to give this vessel the necessary form to break the heaviest ice, the thickness sometimes being as much as 3 feet; she therefore under these circumstances works in conjunction with a twin-screw ice-breaker of the ordinary type of 870 tons displacement and 1,500 indicated horse Power; but when the ice is of moderate thickness, say about 20 inches, the ferry boat is able to work without assistance. These vessels have now been at work for three seasons, and have maintained the railway Service without a single day's interruption. The other important ferry ice-breaker is that which is now being erected on the shores of Lake Baikal, and which when completed will form an important connecting link in the great Siberian railroad, the lake at the point in question being forty miles wide. This vessel has a displacement of 4,200 tons, is 290 feet long, 57 feet beam, and 28 feet 6 inches deep to the rail deck. She is fitted with three sets of engines of an aggregate power of 4,000 horses, two sets being placed aft, driving twin- screw propellers, the third set being at the bow. This vessel has three lines of rail laid on her deck, but as the height of water in the lake does not materially vary, connection with the shore can be made by a movable gangway. As the weather in the lake at times is very stormy it is found desirable that the carriages should be under cover; therefore the vessel is built with a closed superstructure, which gives her very much the appearance of the American lake steamers. In the superstructure is also provided very extensive accommodation for the passengers, who will find it more convenient than being cooped up in the railway carriages during transit. The construction of this vessel marks a record in ship building; the vessel, after being erected ip our yard on the Tyne, was taken to pieces, shipped to St. Petersburg, and thence taken a distance of about 5,000 miles overland to the shores of Lake Baikal, which would have been difficult enough had there been railway transit the whole distance, where- as a considerable portion of the road had to be covered by sledge, and this, considering the great weight of parts of the machinery, and includ- ing as it did her fifteen main boilers, was a task of some difficulty. The vessel is to be launched this summer, and to be ready for next season. __In conclusion, I can only reiterate my belief that the employment of ice-breaking vessels has not yet reached anything like the importance that it will yet achieve, and that still more important developments in this class of vessel may 'be expected in the future. HYDRAULIC DREDGE FOR RIVER WORK. _ Capt. Chester Harding, United States engineer at Grand Rapids, Mich., will on August 28 open bids for the construction of a hydraulic dredge for service in the improvement of Grand River, Mich. The dredge will be wooden hulled and of not more than 30 inches draught when equipped for work. The craft will be capable under ordinary service con- ditions of dredging continuously at the rate of 400 cubic yards per hour, measured in place, of sand, mud or other ordinary material that can readily pass the pump and 'be discharged hydraulically, from a depth of 15 feet or less below water surface and through a discharge pipe 500 feet long, resting on floats. The dredge will be manceuvred up stream by means of two wire cables attached to mooring piles and wound by steam power upon drums located on the dredge. A spud will be provided in the axis of the dredge near the stern, fitted with an iron shoe and furnished with suitable means for its operation 'by steam power. The suction pipes will be forward and the discharge pipes will pass from the pumps into the hold and thence aft to the stern of the dredge, where they will unite by easy curves into a single pipe of cross section equal to the combined areas of cross section of two pipes. The hull is to be of white oak and the freeboard will be not less than 2 feet. The thickness of sides and bottom planking is to be no less than 3 inches and the deck plank will be of white oak of a uniform width of 6 inches and a thickness of 3 inches. The space inclosed-on the main deck will include a machine and tool shop, store room, and coal bunkers. of a capacity of 48-hours' supply of coal. A cabin on the boiler deck will afford accommodation for a crew of twenty men, and provision will be made for office, mess room, state rooms, kitchen, pantry, store room, ' lavatories, water closets, etc. - Two main pumps of equal capacity will be provided. Each is to be of the single-suction centrifugal type of one-half the required capacity of _the dredge. The pump runner is to have detachable soft steel blades, which may be readily removed in the event of breakage, and arrange- ments are to be made for the free entrance of the dredged material from the suction pipe into the center of the pump unobstructed by the rotating wings of the runner. The two pumps will be operated by a single engine, and the pump shafts will be connected to the engine shaft in such manner that each may be promptly thrown out of gear in case it becomes ob- structed from any cause. The main engine which is designed to drive the pump runners, will be horizontal but may be either simple or com- pound at the option of the bidder. Separate engines will be provided for moving the dredge, hoisting the suction, working the spud and operating the steam capstans. A separate engine and drum will also be provided for winding each 1,000-foot wire cable, which will be utilized in pulling the dredge up stream. This latter engine will be capable of pulling the dredge against a current of 3 miles an hour at a speed of 30 feet per minute. The main boilers are to be set up in a single battery and will have a working steam pressure of 150 pounds per square inch. The dredge is to be completed and ready for service by April 1, 1900. SUBMARINE TORPEDO BOATS. Representatives of the Holland Submarine Torpedo Boat Co. have notified the secretary of the navy that they are ready at any time for the final test of the submarine torpedo boat Holland by the naval officials, and Secretary Long kas stated that he will in the near future set a date for the test. In all previous trials dummy torpedoes have been used, but in the coming test a real Whitehead torpedo will be used, and upon the ability of the vessel to strike and destroy a target will depend her chances of acceptance for servize in the United States navy. Trials of the boat in the vicinity of New York during the past week have been in some respects highly satisfactory. The boat was submerged and run for a mile under the surface. At the first trial the-sinking, which was accomplished by letting five tons of water into the midship tanks, was done in 7 seconds and on the second trial in 9 seconds. Two ther- mometers were used in taking the temperature while the boat was under water, and in each case 81 degrees Fahrenheit was indicated. When floating on the surface the temperature in the boat was 77 degrees. Dur- ing most of the journey under water an even keel was maintained, and in spite of tides and currents the course was kept straight. The Holland company wishes to remove all the machinery from the Plunger, another boat of earlier design, building at the Columbian Iron Works, Baltimore, Md., and substitute an entire new installation. Their proposition is being considered by the naval board appointed to inspect the machinery. The board consists of Constructor William H. Varney, Lieut. Frances Haessler and Lieut. D. C. Redgrave. There is a strong probability that permission will be granted.