58 



ANIMAL MECHANICS. 



And, finally, 



1.303 + 2.051 1 

 32.2 ~" 9^60 



In other words, at the pace of 1 1.7 ft. per second, the re- 

 sistance to horizontal motion is -g.-Joth of the weight, accord- 

 ing to the results of the experiments of Messrs. Weber. Hence 

 the work done per ounce, per minute, in Lieutenant Rankine's 

 experiment, is — 



w , 276 x 1 1.7 x 60 „, w 



Work = — — z =0 e. 1 10 ft. lbs. 



9.6 x 575 DD y 



From the foregoing example, it appears that the rate of 

 work done in carrying half one's weight at 8 miles an hour is 

 more than double the work done in a boat race, although it 

 is considerably less than the work done in statical work, by 

 muscles sustaining weights, as already described. 



The following examples, among many others, may be 

 given of the daily amount of work given out, in ordinary la- 

 bour, by the muscles of man : — 



Example^ No. 4. — The useful work, measured by the bricks 

 lifted per day, done by a Dublin hodman, amounts to 181 ft. 

 tons ; to which must be added the fatigue work done in lifting 

 his own weight and that of his hod up and down the ladders. 

 I have observed the hodmen in Dublin to make 40 ascents per 

 day of ladders 40 ft. high ; if,, therefore, we assume the weight 

 of the labourer and his hod to be 170 lbs., we have, 

 Work done in mounting = 170 x 40 x 40 = 272,000 ft. lbs. 

 ,, descending = one-half, . . 136,000 ,, 



Hence, 



408,000 



Fatigue work = 4 , Q ^ 00 f > = x 82 ft. tons. 

 2240 



Useful work, . .181 „ 

 Total, . . . 363 ft tons. 



