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1901.) | MARINE REVIEW. 15 resistance for a model of any given form, and by the law of comparison the resistances of a ship of similar form. In practice each model is driven through the water at successive, appropriate and uniform speeds. During this run a dynamometer furnishes automatic and accurate records of the resistances encountered and of the speed made. In order to render the separate and the successive results intelligible and easy to employ, a curve known as the "curve of resistance" of any particular model is laid down graphically. This curve expresses for a model of particular form the law of its resistance in terms of its speed. By means of previous experiments the force necessary to draw one square foot of the model's immersed sec- tion, or 'wetted skin,' was known. If, then, the number of square feet of immersed skin in the model is calculated, the total skin resistance may be found by multiplying the force required for one square foot by the total square feet of immersed area. If on the curve of skin resistance be laid a second curve representing the whole resistance at low speeds it will be seen that these two curves are practically identical. On this similarity has been based Froude's first law--that the resistance of tolerably fine ships moving at moderate speeds is almost wholly due to surface friction, or to the friction due to the particles of water that rub on the immersed surface. When a model is made to move speedily it is noticed that a train of waves is put in motion and that the size of these waves increases with the velocity of the model. After constructing the curve of resistance at high speeds and comparing it with that of low speeds it will be found that the former has risen-- indeed, in some cases it has shot--much above the curve of low speed or skin resistance. This indicates the entrance into the problem of a new force, and it is now accepted that this excess in great degree measures the force exerted in that "wave making"? which at high speeds is the most important resistance evolved. In these experiments the instruments employed were, first, a tank or basin, sufficiently long for the models to attain the requisite uniform speed; second, "an exquisitely devised apparatus," as an enthusiast terms it, to NEW SHIP BUILDING PLANT AT CHESTER. Philadelphia, Pa., Aug. 14--Within a very few days it is expected that the plans of the incorporators of a company said to be capitalized at $3,000,000 to build ships on the Delaware river, will be made public. It has been generally known for several weeks in this vicinity that a new plant was proposed for Chester, Pa., 12 miles below this city, but the promoters have been so reticent concerning details that came to light re- garding the scope of the scheme. The land optioned consists of from fifty-five to sixty acres on the river front in the heart of Chester. It has a water front of about 2,400 ft. and at present is clear of obstructions. The depth of water in front of the property is from 20 to 25 ft. on the bulkhead line, allowing vessels of the largest size to be docked without much dredging. About thirty acres of the land is owned by the River Front Improvement 'Co. of Chester, which is composed of many of the most influential citizens of that place, including John B. Roach, president of Roach's ship yard; J. Frank Black, president of the Chester National bank; W. C. Sproul, president of the Seaboard Steel Casting Co.; Josiah Smith, district attorney, and several others. One of the leading factors in the new concern is Senator W. C. Sproul of Delaware county, who represents the largest investors. The Arthur Sewall estate, which has a controlling interest in the Bath Iron Works of Bath, Me., will be the largest single stockholder in the new corporation, and this interest will be represented by Arthur Sewall, Jr., executor of the estate. It is said that the formation of this new concern will mean the con- solidation, or at least the working in harmony of the Wetherell, Engine Building Co. and the plate and steel industries of Chester. A yard such as is contemplated will give employment to 1,500 men when running at its normal capacity, and this number will easily reach 2,000 if the yard is fortunate in securing contracts. It is claimed by those close in touch with the enterprise that $2,600,000 of the stock has already been subscribed. Milwaukee. record automatically with electric contacts the speed and resistances of the models, and, third, the tank models. : The experimental tank of the Denny firm at the Leven ship yard is 300 ft. long, in 250 ft. of which length it is 22 ft. broad and 10 ft. deep. The remaining 50 ft. of length, divided into two shallow docks, one at each end, are used for ballasting, trimming and handling the models con- veniently. A double line of rails, 3 ft. 4 in. apart, is carried on suitable beams and girders over the fore and aft center of the tank, and two car- riages, one known as the dynamometer truck and the other as the screw truck, are drawn on these rails by means of an endless wire rope that is moved by an ordinary two cylinder engine. The dynamometer truck is used to ascertain the resistance of the model; the screw truck to record the thrust of the screw, the number of screw revolutions, the slip of the screw and the turning force needed to drive the screws. These instruments are all extremely delicate. The levers are hung either on knife edges or on flat springs, and the wheels in the screw truck work on ball bearings or over Atwood pulleys. The pre- cision and delicacy of these instruments must be extreme, because the quantities dealt with, especially at low speeds, must be measured within one-tenth of one per cent. ARMOR PLATE SUCCESSFULLY TESTED. Two successful tests of armor plate, one for the battleship Maine and the other for a Russian vessel, were conducted at Indian Head last week. The American armor tested was a 6-in. Krupp plate, representing the first group of such armor manufactured by the Bethlehem Steel Co. for the new battleship. Three shots were fired from a 6-in. gun at a velocity of 1,900 ft. per second. All the projectiles were broken on impact. The plate showed a very high resisting quality and proved equal to any ever tested at the proving grounds. As a result of the test the group of armor plate, representing about 400 tons, designed for the Maine, which is now building at Cramps, Philadelphia, will be shipped there immediately. The Russian test was of a 10-in. Krupp plate manufactured by the Bethlehem Steel Co. for the Russian government, representing a group of armor of 800 or 400 tons, intended for the Russian imperial vessel Emperor Alex- ander III. At this plate three shots were fired from a 10-in. gun with a velocity of 1,739 ft. seconds. The plate was highly satisfactory, and the plate bore every evidence of fully meeting the requirements. The Harlan & Hollingsworth Co., Wilmington, Del., launched the new steamship Pathfinder this week. Illinois. Cadillac. OF THESE THREE YACHTS THE CADILLAC WAS SELECTED TO CONTEST FOR THE CANADIAN CUP. Copyrighted by Detroit Photographic Co. Chester possesses many advantages as a ship building site. The river is practically open for twelve months in the year and the work can always be carried on. Almost in the proposed new yard is the plant of the Tide- water Steel Co., which makes all kinds of steel castings and plates, and within easy reach is the large engine building works of the Wetherell Machine 'Co. and those of the Chester Steel Castings Co. OUR TRADE WITH GERMANY. Récent discussions regarding the commerce between the United States and Germany lend especial interest to some figures just presented by the treasury bureau of statistics, which show the growth of commerce between the two countries in the last thirty years, and in detail during the last ten years. These figures show that imports into the United States from Germany have increased from $27,000,000 in 1870 to $100,- 000,000 in 1901, and that exports from the United States to that country have increased from $42,000,000 in 1870 to $191,000,000 in 1901--an in- crease of nearly 300 per cent. in imports from Germany and of nearly 400 per cent. in exports to Germany. On the export side, the greatest growth has been during the last five years, in which time our exports to Germany have doubled, being in 1896 $97,897,197, and in 1901 $191,072,252. This growth is distributed among a large number of articles. Comparing our exports to Germany in 1895 with those of 1901, corn has increased from $1,672,539 in 1895 to $17,305,229 in 1901; wheat, from $1,522,736 to $7,871,- 573; lard, from $8,018,516 to $18,700,875; oil cake and oil cake meal, from $2,339,885 to $5,242,624; flour, from $740,264 to $2,011,259; agricultural implements, from $556,914 to $2,677,319; and copper, from $1,604,390 in 1895 to $7,785,496 in 1901. Machinery of all kinds, including steam en- gines, increased from $1,595,185 in 1895 to $8,109,095 in 1900, the figures for 1901 in this item being not yet available. On the import side, the arti- cles which show the greatest growth during the last decade are coal tar colors and dyes, chemicals, laces and embroideries, earthen, stone and chinaware, and sugar. Coal tar colors and dyes have increased from $1,272,275 in 1891 to $3,822,162 in 1900; other chemicals, trom $1,868,988 to $3,968,116: laces and embroideries, from $945,186 to $2,402,372; earthen, stone and chinaware, from $1,475,057 to $2,787,163; and sugar, from $7,209,150 to $12,846,734. : An examination of the statistics issued by the German government shows that articles from the United States formed in 1891 10.4 per cent. of her total imports for consumption, while in 1900 they formed 16.9 per cent. Of her exports, those to the United States in 1891 formed 10.7 per cent. of the total, and in 1900 9.3 per cent.