128 REPORT— 1859. 



coefficient of dynamic economy with reference to coals deduced from the 



V 3 DS 



formula (w being the consumption of coals per hour expressed in 



cwts.) becomes 11210. 



It will be observed that in Table C the tabulated sizes of ships, as deter- 

 mined by their respective load displacements, increase progressively from 

 250 tons displacement up to 25,000 tons, showing under assumed conditions, 

 which, however, are justified by now realized advancement in ship and 

 engine construction, the mutual relations of displacement and coals cal- 

 culated for the speed of 10 knots per hour as most convenient for a standard 

 of reference. The intended practical use of this Table C is to facilitate 

 mercantile investigation into the dynamic merits of steam-ships as locomotive 

 implements of burden by comparing their actual consumption of fuel with the 

 calculated consumption of the ship of corresponding size and speed as recorded 

 in this tabulated standard of comparison, whence the constructive merit of 

 ships, as respects their working economy of fuel, on which the cost of freight 

 so much depends, may be relatively ascertained. For example, a certain ship 

 of 800 tons mean displacement attains the speed of 8*8 knots per hour, with 

 a consumption of coals certainly not exceeding 4*3 cwt. per hour, or *49 cwt. 

 per nautical mile or knot; which (as the consumption of coals per knot varies 

 cateris paribus as the square of the speed) is equivalent to '63 cwt. per knot 

 at the speed of 10 knots per hour. Now by referring to Table C, we find 

 that on the assumed data therein referred to, the standard ship of 800 tons 

 displacement, steaming at 10 knots per hour, would consume *77 cwt. of coal 

 per knot. Hence, therefore, it appears that the ship referred to in this 

 instance is superior to the tabulated standard in the proportion of - 77 to *63, 

 that is, in the proportion of 122 to 100, the superiority with reference to the 

 consumption of coals per knot being 22 per cent. 



Again, a certain ship of 3500 tons mean sea displacement makes a voyage 

 at the average speed of 12*88 knots per hour, consuming 83 cwt. of coal per 

 hour, or 6*44 cwt. per knot, which, by the law of dynamics above quoted, is 

 equivalent to 3*88 cwt. per knot at the speed of 10 knots per hour; but by 

 referring to the Table of comparison C, we find that the standard ship of 

 3500 tons displacement, steaming at 10 knots per hour, would consume only 

 2 - 06 cwt. of coal per knot. Hence, therefore, it appears that the ship re- 

 ferred to in this instance is inferior to the tabulated standard ship in the pro- 

 portion of 2 - 06 to 3'88, that is, in the proportion of 53 to 100, the inferiority 

 with reference to the consumption of coals being 47 per cent. 



Thus, by reference to this tabulated standard of comparison (C), we have 

 the means of readily deducing the exact per-centage by which ships, as 

 respects the dynamic duty performed with reference to the consumption of 

 coals, differ from each other. I need not dwell on the importance of this 

 consideration as affecting the commercial value of ships for sale or charter. 



With reference to Table D, showing the mutual relations of displacement, 

 power, and coals consumed per day, per hour, and per knot for the respective 

 speeds of 10, 15, 20, aud 25 knots per hour, the object of this Table is to 

 show the extent to which the required engine-power, and the nautical mileage 

 consumption of coals are dependent on the rate of speed, thereby facilitating 

 the adaptation of ships as respects their size and power to the service that 

 may be required of them. 



For example, by referring to Table D, we observe that a ship of 5000 tons 

 displacement, steaming at 10 knots per hour, requires 1170 indicated h. p., 

 and consumes 2 - 61 cwt. of coal per knot; but to steam 15 knots per hour, 

 the same vessel would require 3947 ind. h. p., and the consumption of coals 



