THE COPLEY MEDALIST OF 1871 455 



published a memoir which far transcends his first one in 

 weight and fulness, and, indeed, marks an epoch in the 

 history of science. The title of Mayer's first paper was, 

 "Remarks on the Forces of Inorganic Nature." The title 

 of his second great essay was, "Organic Motion in its 

 Connection with Nutrition." In it he expands and illus- 

 trates the physical principles laid down in his first brief 

 paper. He goes fully through the calculation of the me- 

 chanical equivalent of heat. He calculates the perform- 

 ances of steam-engines, and finds that 100 Ibs. of coal, in 

 a good working engine, produce only the same amount of 

 heat as 95 Ibs. in an unworking one; the 5 missing Ibs. 

 having been converted into work. He determines the use- 

 ful effect of gunpowder, and finds nine per cent of the 

 force of the consumed charcoal invested on the moving 

 ball. He records observations on the heat generated in 

 water agitated by the pulping-engine of a paper manufac- 

 tory, and calculates the equivalent of that heat in horse- 

 power. He compares chemical combination with mechan- 

 ical combination the union of atoms with the union of 

 falling bodies with the earth. He calculates the velocity 

 with which a body starting at an infinite distance would 

 strike the earth's surface, and finds that the heat gener- 

 ated by its collision would raise an equal weight of water 

 17,356 C. in temperature. He then determines the ther- 

 mal effect which would be produced by the earth itself 

 falling into the sun. So that here, in 1845, we have the 

 germ of that meteoric theory of the sun's heat which 

 Mayer developed with such extraordinary ability three 

 years afterward. He also points to the almost exclusive 

 efficacy of the sun's heat in producing mechanical motions 

 upon the earth, winding up with the profound remark, 



