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THE MARINE RECORD. IN THE ENGINE ROOM the block shown in Fig. 2 to be substituted for the block . B. If it be towed through the water, it will, owing to —————= its shape, displace the water gently. But, assuming the areaa 4cd to be equal to the area of the surface 4’ Fig. 1, the water displaced by the two blocks will be the same for equal speeds and equal in- crements of time. As the water is displaced gently by “32 : ythe block \ shown in Fig. 2 , less weight on the end of the ‘string C and, and hence, less power is re- quired to move it a given distance at the rate of one inch in one second. But, if the speed is doubled, it will be found that the force is increased in the samc proportion as in the first case considered; that is, four times the weight is requlred. Let us apply the law to a practical example. A vessel fitted with an engine developing 800 net horsepower, has a speed of 15 miles per hour. How much would the power of the machinery have to be increased to’ propel the vesselgt the rate of 17 miles per hour? Applying the law, we have the following proportion: 15% : 17% :: 800 : the required horsepower. That is, 3,375 : 4,913 :: 800 : 1,164.56. Thus it is seen that to increase the speed two miles per hour, the power of the machinery must be increased 1,164.56—800—364.56 net horsepower. In practice, however, as the friction of the hul! of the vesselis not constant at all speeds, also, as the efficiency of the machinery as well as the propelling insirument is not the same at all speeds, ac- cording to circumstances, slightly more dr less power than calculated, may be required for the desired increase in speed. RELATIONS OF POWER AND SPEED. Many marineengineers do not understand why the power required to propel a vessel varies of the cube of the speed says Home Study. The following it is hoped will make this clear: Suppose we have a tank nearly filled with water, as shown in Fig 1. Floating within the tank, and weighted down so as its'upper surface is at the water level, is a block of wood 8 in the form ofacube. This block may be towed through the water in a direction perpendicu- lar to its surface 2’ by means of the string C which passes over two.small pulleys at the right hand end of the tank, as shown. To the free end of the string a weight W may be attached. Since two bodies cannot occuby the same space at the same time, when the block moves through the water, it displaces the water in front of it, which closes in again behind. The volume of water displaced in a certain time when the block is in motion, is evidently the product of the area of the sur- face B’ and the distance the block moves within thaf time. For instance, if the surface 4’ be one square foot the volume of water displaced in one second at a speed of one foot in one second, is one cubic foot; at a speed of two feet in one second, two cubic feet, and so on. In order to move the block through the water, a force which in this instance is supplied by the weight VY must be applied to the block. It will be understood that the force necessary to move the block at a certain speed is the measure of the resistance of the water against the block at that speed. Assume that a weight of three pounds attached to the string C was found necessary to tow the block through the water at a uniform rate of one inch in one second; then, in 120 seconds the block will move a distance of 120 inches. Therefore, since work is the product of force into distance, and since the force in this case is three pounds and acts through a distance of 12° — 10 feet, the work done is 103=—30 foot- pounds. As this amount of work is done in 120 sec- oR) Mi =e ieee a Fie 2. BOILER FEED PUMPS. In order to get the size of boiler feed pumps we have to know the amount of water we require. We wiil take for our boiler one having 15,000 feet of -heating surface; under favorable circumstances this would be reckoneda 100 H. P. boiler. -The standard adopted by the A. S. M. E.. for the horse-power of boilers—the hourly evaporation of 30 pounds of feed water at 100° F., into steam at 70 pounds gauge pressure—has the advan- tage of approximating very closely to the requirements of the modern stationary engine. As 30 pounds of water equals 3.6 gallons for each horse-power per hour, a 100-horse-power boiler will require 100 times as much, which - would be 360 gallons per hour. In proportion- ing pumps, however, it is well to remember that boiler work is seldom perfectly steady, and that as the engine cuts off just as much steam as the work demands at each stroke, all the discrepancies of demand and supply have to be equalized in the boiler. Therefore, we may often have to evaporate during one- half hour from 50 to 75 per cent more than the normal requirements. For this reason it is sound policy to ar- range the pumps so that 630 gallons per hour, or 10.5 gallons per minute, may be handled by them without undue speed or friction. TM Dui | ae Ty id a Hn itty tli " HH onds the horsepower necessary to do this work is BO 5 AO gi eee horsepower, 33,000 K 120 ~~ 2,200 : Thus it is see that under the above assumption g945 horse power is required to tow the block of wood through the water at a speed of one inchin one second fora dis- tance of 120 inches. : We will now find what weight must be attached to the string to tow the block at the rate of two inches in one second, or twice as fast in the former case. By trial, it will be found that 12 as fast in the former case. By trial, it will be found that 12 pounds are required to give the desired velocity. Thus it is seen that to double the speed four times the weight was neccessary from which the general law may be established, that the resistance to a body moving through water varies as the square of the velocity. Had the velocity been quadrupled, it would have been found that 423=—48 pounds would have been required. In the above case as the block now moves twice as fast, it will cover a distance of 120 inches in one-half of the time; z. ¢., in 60 seconds. ‘The work done in that time is 1210—120 foot-pounds, and the horsepower necessary to tow the block through the water at a speed of two PITCH OF PROPELLERS. Engineer, New York, makes the following repiy to a New York correspondence who inquires: ‘‘How is the pitch of the screw arrived at for high-speed boats? In other words. If I want to make a boat go twenty miles per hour how shallI pitch the screw? — The pitch is fixed by the number of revolutions the engine is to make for a given speed. Suppose it is de- sired to run the engine at 300 revolutions per minute for a speed of 20 miles per hour, then assuming the pitch to be 6 feet the vessel would advance 1,800 feet per minute, neglecting slip. In 20 miles there are 105,000 feet (5,280x 20) so that 1,800 feet per minute would give us 108,000 feet advance in one hour, neglecting slip. As this last inches in one second a distance of 120 inches is . fully 20 ; Or ean is fully 20 per cent. in small wheels we must add 20 per i cent. for it, making the pitch 7 feet 2% in. The diame- Sa we orsepower, ter of the screw is another’ consideration and the usual x 2 practice is—diameter equals three-fourths of the pitch. SEE oe JAPAN proposes to build up her commercial navy by giving subsidies to shipbuilders for eyery ton above 1,000, and to ship owners for all ships of 1,000 tons that can make ten knots an hour, the subsidy being increased for every 500 tons additional burden or every knot addi- tional speed. But, as 94, divided by s455—8, it is seen that in order to double the speed of the block, eight times the amount of power is required. From the above experiments the following general law may be deduced: The power re- quired to propel a vessel varies as the cube of the speed. In order to show that the shape of the block does not in- fluence the results arrived atin the experiments, assume -be furnished until the men are mustered and have signed PROVIDING FOR THE NAVAL RESERVE. Congressman Jenkins, of Wisconsin, has introduced. in the House the following bill, No. 5555, which was re- ferred to the Committee on Naval Affairs. Its text is as follows:— Whereas, House bill 10,622, introduced June 26, 1888, providing for the enrollment of naval militia and the re- organization os naval forces, made it lawful in States and territories bordering on the sea and lake coast and navigable rivers to enroll and designate, as the naval militia all seafaring men of whatever calling, and all men engaged in the navigation of the rivers, lakes, and other waters, together with shipowners and their em- ployes, yacht owners, members of yacht clubs, and other associations for aquatic pursuits, and all ex-officers and former enlisted men of the navy. Whereas, although this measure did not become a law, it was made the basis of law in various States, and. on March 1, 1895, there were enrolled in 13 States a na- val militia of 2,695 enlisted men; Whereas, the States of Ohio, Indiana, Wisconsin and Minnesota have no organization of naval militia, and the naval militia of the States of New York and Penn- sylvania are located in the seacoast cities of those States, leaving for the protection of the shipping and cities of the Great Lakes only the naval militia of Illi- nois and Michigan, numbering 387 men; Whereas, the report of the Secretary of the Navy for 1895 calls attention to the fact that the number of men allowed by existing laws are all in active service, and it is proposed to keep as first-class reserve certain vessels of the navy for which no regular crews are provided; Whereas, the organizations of naval militia under the different State laws are somewhat restricted by State lines, and there is no especial provision for these forces being called into the service of the general government; now therefore, Be it enacted, etc., That the Secretary of the Navy be authorized to encourage organizations of national naval volunteers in all States bordering upon the Great Lakes, and to draw up such regulations for their enlistment and government as shall, in his judgment, conduce to — uniformity and efficiency. 2—That the Ordnance Bureau of the Navy be author- ized to furnish for the defense of lake cities and the use — of naval volunteers such ordnance, machine and rapid- — fire guns, boat howitzers and other small arms as the Secretary of the Navy may approve; provided, that said arms of all, kinds shall remain the property of the United States, subject to the order of the Secretary of the Navy, and shall only be supplied when ‘proof is fur- nished of the enlistment of a sufficient number of suit- ~ able men in accordance with the regulations of the Navy Department. Se 3—That the Secretary of the Navy be authorizedto furnish each of the national volunteers one blue uni- — form and one pea jacket such as are worn by the sea- men of the navy; provided, that no such uniform shall enlistment papers such as the Secretary of the Navy shall furnish, and for not less than one year’s service. 4—T hat such national naval volunteers shall receive no pay or compensation from the government other than the uniforms, except when called into the service of the United States, when their pay and rations shall be those of the navy. 5—That the Secretary of the Navy is hereby author- ized to detail ensigns or lieutenants of the junior grade to drill such national naval volunteers whenever in his judgment it is advisable; but when called together for drilling purposes the said volunteers shall not be con- sidered as called into the service of the United States, unless they are required to leave their places of enlist- ment. The Secretary of the Navy is also authorized to detail a paymaster to take up the accounts, disburse the’ — funds, and issue the clothing as required by this act. 6—That the enlistment papers signed by said national naval volunteers shall subject them to the orders of the President of the United States and the Secretary of the Navy for service in time of war, either afloat or on the shore, and either for defense of the commerce of the Great Lakes, or for manning the vessels of the navy. 7—That to:secure the rapid enlistment of such naval volunteers and the completion of their organization be- fore the opening of navigation the Secretary of the na- vy is authorized to employ one or more suitable persons and, if he deems it expedient, to have an office in one of the lake cities, with the necessary clerical assistance, the head of such office to be some citizen well acquain- ted with the commerce of the Great Lakes, and of some naval or military experienoe, the pay of snch official to be that of a commander. 8—That for the purpose of promptly and efficiently carrying out the purposes of this act the sum of $25,000, or such portion thereof as may be necessary, is hereby appropriated. bee eo - ie oan WB a ge “e 3 <a 53 a teh OEE ar TURKISH complications have apparently made Russia even more desirous of completing her railway, and to accomplish this object that government has sent an agent to negotiate with American contractors. This agent, who was lately in Seattle, is Count De Tolance, a civil engineer, and is said to be conferring with a San Francisco firm, with the object of letting a contract for the construction of part of the road.