676 DYNAMICAL AGENCIES OF CALORIC 



6 Ibs. of carbon and hydrogen by respiration in 

 twenty-four hours, and perhaps about 3lbs. during 

 eight hours' vigorous exercise. From which it 

 follows, (if these data be an approximation to the 

 truth,) that thirty-three such horses would con- 

 sume about lOOlbs. of carbon and hydrogen by 

 respiration in eight hours ; and that they would 

 generate an aggregate force equal to the eleva- 

 tion of 550,000,000 Ibs. a foot high, or above five 

 times what is created by the combustion of 100 Ibs. 

 of coal in the furnace of a Cornish engine. 



In every description of mechanism, the power 

 generated is always directly in proportion to the 

 quantity of the impelling agent, ceteris paribus. 

 As the velocity of a steam-car depends on the 

 amount of caloric communicated from the furnace 

 to a given quantity of water in the boiler, and 

 thence to the piston, so is the locomotive power 

 of animals determined by the amount of the same 

 active principle imparted to blood in the lungs, 

 and thence to every part of the body. Nor is 

 this any more remarkable, than that the velo- 

 city of planets through their orbits, like all the 

 changes and transmutations which make up the 

 history of chemistry and geology, should be di- 

 rectly in proportion to the heating influence of 

 the sun. 



But as it is an universal law of nature, that the 

 cause of force is always expended in producing 

 motion, the caloric which is employed in uniting 



