44 THE MECHANISM OF LIFE 



And that is why there is always waste, or loss of available 

 energy, and it is why the capacity for doing work tends to 

 diminish indefinitely in the universe as we know it. 



Quantitative Energy Transformations. — The following state- 

 ments are the actual results of experience: 



(a) 1 horse-power^^^SfiOO foot-founds per minute. 



That is to say, the amount of mechanical work that would be 

 done against the earth's gravity when a mass of 33,000 pounds is 

 raised 1 foot in one minute, or conversely the amount of work done 

 by the earth's gravity when a mass of 33,000 pounds falls 1 foot in 

 one minute, is called a horse-power. Long ago British engineers 

 found, by actual experiments, the strength of an average cart- 

 horse as measured in the above ways, and the quantity so found 

 was, later on, adopted as a mechanical unit. 



(6) 1 ^.p.=0-178 Calorie per second. 



This means that when the work done by a mass of 33,000 pounds 

 in falling 1 foot in one minute is completely changed into heat 

 (which it can be experimentally), 10-8 kilogram of water is raised 

 1° C. in temperature. 



(c) I qram of fat =9-3l„ , . , , 



' J. , ., , ^ Calories, when burnt m 



1 gram oj proteid =4-1 V , , , 



1 gram of carbohydrate— i-l] •^' 



These are statements of the convertibility of chemical sub- 

 1^ stances into heat. They mean that when certain quantities of 

 combustible materials are burned in oxygen, certain quantities of 

 heat are generated. Many more instances might be given. The 

 transformations are complete ones — that is, all the available 

 chemical energy transforms into heat energy. 



{d) 1 kilowatt=0-239 Calorie per second. 



That is to say, when a current is sent through a conductor 

 against a resistance it transforms into heat. Some of the 

 current (=1 kilowatt) disappears, and a certain quantity of heat 

 (=0-239 Calorie) is developed. The heat developed is energetic- 

 ally equivalent to the current that disappears. 



Now, since 1 kilowatt=0-239 Calorie per second, and 

 1 h. p. =0-178 Calorie per second, it follows that — 



(e) 1 kilowaU:=l -34:1 h.p. 



