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September, 1910 16,000 crosses the line for V=2lata value which may be readas 1.55. There- fore, for K= 240, H=1.55 X 16,000 = 24,800. But K = 225. Therefore H = 240 24800 X ---- = 26,453, and 26,500 horse- 220 power should furnish the required speed. 2--D = 9,000; V = 18%; K = 240; H = ? By inspection (between the curves), H/D = 1.27, and H = 11,430. This ship would naturally be provided with engines designed for 11,500 H. P. Another way of getting atcases which do not fall exactly on the lines plotted 4.5 4.0 3.5 3.0 2.5 2.0 15 1.0 0.5 1090 3000 5000 8000 depends upon the relative rates of vari- ation of these various elements. Our first equation shows that H varies as the cube of V, and as the two-thirds Power of D. In other words, for sim- : Hi Vi ilar-formed ships, --- == --- when D Ets Ve ae D*, * constant, and --- == --- when V¥ 1 He D%, constant. When both D and V _ vary, Ay Ve D*, . a , with K_ constant. H, VE) 'THE MarRINE REVIEW Now, variations in both V and D may be expressed in percentages of the quantities themselves, and their effects on H computed in a very simple man- ner which, for all practical purposes, is sufficiently exact. If we designate by V% the percentage variation in V, and by D% that in D, we find that Hi = (1+3V%) X (1+ 2/3D%). The simplicity of the practical appli- cation of this formula is best shown by another example: Let.) 8,300; Ve =e 2045 -- -- -- BASED |ON K= 240 13000 15000 DISPLACEMENT IN TONS Fic: 2: 10000 2. re ee Prom the diagtam: Ho 1007 D = 13,333, when D = 8,000 and VV = 20. Now D% = 3.75 and V%=25; there- ore, es first approximation = 13,338 Correction for D% = (75% 2/3) %o a8 -------- -- Horsepower, second aproximation = 13,666 Correction for V% = (25:..% 3) % 1,025 --__---- 14,691 --_-- -- Horsepower, final approximation = 363 With K differing from the K of our curves, another approximation would be necessary. If we compute the horsepower direct- ly, by means of the Admiralty formula, 410 X 8,615 --- 240 The difference is negligible, for, as a matter of fact, the engines would in all probability be designed for 14,750 or even 15,000 horsepower. The construction of a number of sets of curves on a large scale, each set rep- resenting a definite value of K, would we shall have H x teair. KNOTS 24 14 10 20000 25000 27000 involve considerable "initial" labor in computation and plotting, but the sim- plification which would result on sub- sequent calculations should pay enor- mous dividends on the investment. The Isthmian Canal Commission has awarded contract to William Simons & Co., Renfrew, Scotland, for a steel sea- going ladder dredge for service at the Pacific entrance of the Panama Canal at $399,340. The other bidders were: Union Iron Works, San _ Francisco, $874,146, and Lobnitz & Co., Renfrew, $449,000.