498 PHYSIOLOGY AT THE FAKM. 



A few words will suffice to indicate how far such an opera- 

 tion is within our reach. It is believed that one ounce of pure 

 carbon, yielding, with oxygen, 3.66 oz. carbonic acid, evolves, 

 during combustion, heat enough to raise the temperature of 

 14,200 times its weight of water through 1 of Fahrenheit 

 that is, of 14,200 oz., or 887.5 Ib. of water.* As every pound of 

 water raised through 1 of Fahrenheit's thermometer indicates 

 the exertion of force equal to that produced by the fall of a 

 pound weight through 772 feet or, what is the same thing, by 

 the fall of 772 Ib. of matter through the height of one foot the 

 consumption of an ounce of carbon in the formation of carbonic 

 acid in the living system shows an amount of work performed 

 such as is equivalent to the effect of 887.5 Ib. falling through 

 772 feet, or to that of 685,150 Ib. falling through one foot. 

 If there be 7 oz. of carbon consumed daily in the formation of 

 carbonic acid in the living body, the total corresponding work 

 vital, heat, mechanical, and mental will be represented by a 

 force equal to that obtainable by the fall of 4,796,050 Ib. through 

 one foot. If, as some think, there be 10 oz., or even more, so 

 consumed, then the total work will be represented by the fall of 

 6,851,500 Ib. through one foot or, friction apart, to the rais- 

 ing of that number of pounds through the height of one foot. 

 According to some authorities, as much as one-third of the 

 daily force of the frame is absorbed in the action of the heart 

 alone ; so that, when that and the other parts of vital work, 

 the mental work, and the heat work are deducted from, the 

 above largest number, 6,851,500, there may not be a much 

 greater estimate of the external mechanical work of which a 



man is capable than what is brought out by a wholly practical 



, ,. . , . , . f 6,851,500 

 mode of investigation, for -* = 1,712,875. 



Total carbon in the food nearly a measure of the total energy. 

 According to Professor Playfair, the number of foot-pounds, 

 * Miller, ' Elements of Chemistry,' part iii. p. 854. 



