RESISTANCE OF STEAM VESSEL WITH PLANE SURFACE. 77 



146 to 2150, or as I to 15 very nearly, which exactly agrees with the number given in the 

 table. The agreement is equally close in the Flamer ; and the mean obtained this way from 

 the whole set of experiments is very nearly the same as that given in the above table. 



In this calculation the actual power of the engine is assumed equal to the nominal power ; 

 but it may slightly exceed it, but the degree will not be much when the loss from the air, 

 friction, 8tc., are deducted. 



The valuable experiments on resistances made by the late celebrated Colonel Beaufoy, and 

 presented to his scientific countrymen, in a truly liberal manner, by his son, Henry Beaufoy, 

 Esq., enable us to put a third test upon the accuracy of the preceding deductions; 

 and it is very satisfactory to be able to confirm those extraordinary results on the authority 

 of his tables. 



It has been found above, that to urge a plane section 263 feet area at the rate of 11 '33 

 English miles, or 9'84 nautical miles, per hour, through still water, would require 2150 horse 

 power. According to Colonel Beaufoy's results, it would require a power of 2444 horses, 

 which would give a still less fraction than a fifteenth ; but compared with a cylinder with flat 

 ends, the number of horses power is 2275, and the fraction greater than one-sixteenth, but less 

 than one-fifteenth, a confirmation which one could scarcely have hoped to have obtained. 



These results are deduced as below. According to Colonel Beaufoy's experiments, 

 (Table 1. Part in.,) it requires a force of 203'79 Ibs. to urge a plane of one square foot 

 through still water at the rate of eight nautical miles per hour, or 810 feet per minute : now 

 the Medea moved with a velocity of 11-33 miles per hour, or 966 feet per minute ; it would 

 therefore require, according to Colonel Beaufoy, (the resistance being as the square of the 

 velocity,) 



810* : 996 2 :: 203-79 Ibs. : 308 Ibs. 



Now the section being 263 feet, the resistance per foot 308 Ibs., and the velocity 996 feet 

 per minute, 



308 x 996 x 263 



33,000 = 2444 ' 



the number of horse power requisite to urge a plane section of this area at the given rate : 

 but if, instead of a mere plane, we take Colonel Beaufoy's experiments for a cylinder with 

 flat ends, we obtain the number of horse power 2275, as above stated. 



If the results of Colonel Beaufoy's experiments had been made use of throughout the pre- 

 ceding investigations, the numbers in column 17. of Table II., and in column 4. of Table XII., 

 would have been increased by about one-seventh ; and in estimating the power exerted on the 

 paddles it would have been found to exceed the nominal power of the engines, which proves 

 that engines work above the nominal power. 



[NOTE. In the paragraph at the foot of page 51, the author of this excellent paper appears to have disregarded the 

 inclination of the paddle-board with the radius, as far as it affects the power developed by the engine, and this will 

 have some degree of influence on several of his results. This was suggested to the author when the sheet was in the press, 

 and some explanatory remarks are appended at his request. If the tangential resistance to the motion of the wheel were 

 equal to the resistance to the transmission of the vessel, the ratio of the useful to the whole effect, would be precisely 

 that of the velocities of the vessel and wheel. But the resistance on the vessel is equal to the lateral pressure on the 

 wheel, and the tangential force by which the engine overcomes it, as the author shows at the top of the same page, 



