ANIMAL MECHANICS. 



57 



Velocity* Proportion of Resistance to Weight. 



Miles per Hour. 



I. I.818 — = — 



32.2 28.27 



2-OCI I 



II. 4.353 — = 



32.2 »5-70 



A.280 I 



III. 10.577 = 



32.2 7.51 



From these results it follows that a man walking at the 

 rate of 1.8 18 miles per hour should travel 28.27 mu es before 

 he has done the work represented by lifting his body through 

 one mile of vertical height. 



If we interpolate between the results I. and II., to find the 



resistance at the pace of 7 miles per hour, we find it to be — — 

 r . 20 - 6 5> 



a result that agrees well with that already found from direct 



measurement of the vertical elevation of the centre of gravity, 



at each step in ordinary walking. 



As an example of the rate of work that may be attained 

 in carrying loads horizontally, I shall give the following, to 

 which my attention was called by Professor Kankine, and 

 which is founded on data obtained by his father, Lieutenant 

 David Eankine : — 



A labourer, supposed to weigh 150 lbs., carrying a load of 

 1 26 lbs. for 30 seconds, can travel at the rate of 11.7 ft. per 

 second (8 miles an hour) ; what is the rate of work done, per 

 ounce of muscle, per minute ? 



At 6.385 ft. per second, the resistance is measured by a 

 loss of velocity of 2.051 ft. per second. 



At 15-513 ft. per second, the resistance is measured by a 

 loss of velocity of 4.289 ft. per second. 



Therefore, 



l J-5 l 3 " 6 -3 8 5 : n.700 - 6.385 : : 4.289 - 2.051 : x 

 or, 9.128 : 5.315 : : 2.238 : x = 1.303 



