10 MATTER, LIVING FORCE AND HEAT. 



lecture) — are mutually convertible into one another. In 

 these conversions nothing is ever lost. The same quantity 

 of heat will always be converted into the same quantity 

 of living force. We can therefore express the equivalency 

 in definite language applicable at all times and under all 

 circumstances. Thus the attraction of 817 lb. through the 

 space of one foot is equivalent to, and convertible into, the 

 living force possessed by a body of the same weight of 

 8171b. when moving with the velocity of eight feet per second, 

 and this living force is again convertible into the quantity 

 of heat which can increase the temperature of one pound of 

 water by one degree Fahrenheit. The knowledge of the 

 equivalency of heat to mechanical power is of great value 

 in solving a great number of interesting and important 

 questions. In the case of the steam-engine, by ascertaining 

 the quantity of heat produced by the combustion of coal, 

 we can find out how much of it is converted into mechanical 

 power, and thus come to a conclusion how far the steam- 

 engine is susceptible of further improvements. Calculations 

 made upon this principle have shown that at least ten times 

 as much power might be produced as is now obtained by 

 the combustion of coal. Another interesting conclusion is, 

 that the animal frame, though destined to fulfil so many 

 other ends, is as a machine more perfect than the best con- 

 trived steam engine — that is, is capable of more work with 

 the same expenditure of fuel. 



" Behold, then, the wonderful arrangements of creation. 

 The earth in its rapid motion round the sun possesses a 

 degree of living force so vast that, if turned into the 

 equivalent of heat, its temperature would be rendered at 

 least 1000 times greater than that of red-hot iron, and the 

 globe on which we tread would in all probability be 



