56 



ANIMAL MECHANICS. 



The angle i has been carefully measured for three diffe- 

 rent velocities by Messrs. Weber, with the following results : — 



Velocity. Inclination of Trunk. 



Feet per Second. Miles per Hour. 



I. 2.667 . . . i. 818 ... 2 0 43' 



II. 6.385 . . . 4-353 ... 7 4o 

 in. 15.513 . . . 10.577 ... 19 13 



If there were no resistance to horizontal motion, the slope 

 of the body would be found by calculation from equation ( 13) ; 

 or, assuming the slope to be given, as measured, we find the 

 velocity from the equation 



v = 32.2 x tan i (14) 



Solving this equation for the three inclinations of the 

 trunk measured by the Messrs. Weber, we find — 



Velocity of Feet per Second. Inclination of Trunk. 



I- 1.528 2° 43' 



4-334 7 4o 



in. 11.224 I 9 *3 



From the preceding results, it follows that the observed 

 velocity is in excess of the velocity calculated on the hypo- 

 thesis of no resistance for fixed inclinations of the trunk, by 

 the following quantities : — 



I. (2.667 - 1.528) = 1. 1 39 ft. per second. 



II. (6.385 - 4-334) = 2.051 



in. (15.513 - 11.224) = 4.289 „ 



The proportion of resistance overcome to weight lifted, in 

 the three cases, is therefore— 



