MERCANTILE STEAM TRANSPORT ECONOMY. 429 



been raised it must be noticed. Undoubtedly, each shipowner has an 

 individual interest in liis own sliips being the best afloat, but if he does 

 possess the best ships, it is equally his interest to keep that fact and the 

 means of acquiring them to himself, so that the charges for freight may con- 

 tinue to be ruled by the inferior dynamic qualities of the average ships em- 

 ployed by the trade, not by the superior dynamic qualities of the best ships 

 as possessed by himself, the difference being the shipowner's private advan- 

 tage or the public's loss. It is therefore the interest of the public that all 

 bad types of shipping be exposed and eradicated. Freight would then, as 

 respects the quality of ships, be ruled by a scale of charges derived from 

 the performance of a generally improved type of ships working in fair com- 

 petition with each other. 



Having already defined the measurement of the units by which we propose 

 to designate the working power of the engines and the size of the ship, 

 namely, ind. h.p. at 33,000 lbs. raised one foot high per minute, and tons 

 weight of displacement at 35 cubic feet of water to the ton, it is now neces- 

 sary that we refer to the received law or formula by which the comparative 

 dynamic duty of steam-ships may be numerically ascertained. The formula 

 usually adopted for obtaining the coefficient of dynamic duty of steam- 



T—T—r — =C ), in which D is the displacement of the ship at the 



time of trial expressed in tons weight, V the speed (usually expressed in 

 nautical miles per hour), and ind. h.p. the working power as ascertained by 

 means of the indicator. The resultant number (C) deduced from this formula 

 is termed the coetficient of dynamic performance. This coefficient (C) will 

 be a constant number for all vessels of perfectly similar model or type of 

 form, and of which the engines are equally effective in proportion to their gross 

 ind. h.p. ; but if the vessels be not of similar type, and the engines not equally 

 effective in proportion to their ind. h.p., the coefficient (C) will vary, and thus 

 the dynamic performance of different vessels will be comparatively ascertained. 

 It is not our purpose in this paper to raise any question as to the scientific 

 rationale or resultant accuracy of this formula ; I will merely observe, that 

 though open to criticism in several respects, the results of experience have 

 demonstrated that this formula, when applied to any known type of ship, ex- 

 pounds the mutual relations of displacement, power, and speed with a degree 

 of precision that admits of its being practically made use of for determining 

 the resultant speed that is to be expected from any combination of power 

 and displacement, and in like manner, any one of the three elements of the 

 formula may be deduced from the other two being given. Further, this 

 formula may be rendered available as a counting-house check on the work- 

 ing operation of steam-ships, simply by substituting the consumption of coals, 

 expressed in cwts. per day of 24 hours (W), in lieu of the ind. h.p.; for 1 

 cwt., or 112 lbs., per day of 24 hours is at the rate of 4"66 lbs. per hour, 

 which is probably about the ordinary consumption per ind. h.p. per hour, 

 and it ought not to be exceeded. If, therefore, in lieu of the ind. h.p. we 

 substitute the consumption of coals, calculated in cwts. per day of 24 hours, 

 the resultant coefficient (C) will afford an approximate indication of the 

 good or bad performance of ships, as compared one with another, and the 

 fact of an inferior performance being thus detected, the cause to which it 

 may be attributable, whether to inferior type of form, or foulness of bottom, 

 or inferior adaptation of engine, or inferior construction of boiler, or inferior 

 management on board ship, will then become the subject of professional in- 

 quiry ; thus, the merchant, by aid of his counting-house statistics of displace- 

 ment, time on passage of given length, and coals consumed, will be enabled 



