52 



THE ANIMAL AS A MACHINE. 



birds of fast or of long flight. A man can exert 0.25 

 horse-power for a few minutes at a time, 0.15 horse- 

 power by the hour — which, at 150 pounds weight of the 

 man, would require 600 to about 700 pounds per horse- 

 power. The horse weighs 1500 or 2000 pounds per 

 horse-power ; but the birds develop power at the rate of 

 probably less than one third those figures for the former, 

 and one eighth or one tenth for the latter. Falcons fly 

 60 miles an hour, pigeons 35 to 60 for hours together, 

 and the albatross accompanies fast steamers thousands 

 of miles without halt or rest. The birds weighing 

 probably 100 to 200 pounds per horse-power can carry 

 for a time an added load of 30 to 50 per cent, as when 

 the carnivorous birds carry away their prey. 



According to M. Fourier, the daily work of a good 

 horse has a maximum, under the best load for each 

 speed, at about 0.90 (2.95 feet) meters per second, or 

 3200 (10.596 feet, 2 miles, nearly), an hour. Taking 

 this maximum as unity, he gives the following as prob- 

 able values of work per pound at other speeds : * 



SPEED PER 



HOUR. 



DAILY W( 



Metres. 



Miles. 





2,000 



1.25 



0.69 



3,200 



2.00 



1. 00 



4,000 



2.50 



•99 



6,000 



375 



.94 



8,000 



5.00 



.83 



10,000 



6.25 



.68 



12,000 



7.50 



.51 



14,000 



8.75 



.33 



16,000 



10.00 



.18 



1 8,000 



11.25 



.07 



* Genie rural, Herve Mangon ; t. iii., p. 175. 



