THE COPLEY XEDALI5T Or 1571. 433 



briefpaper. He goes fully through the calculation of 

 the mechanical equivalent of heat, He calculates the 

 performances 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 nnworking one; 

 the 5 miasthig Ibs. having been converted into 

 He determines the useful effect of gunpowder, and 

 nine per cent, of the force of the consumed charcoal m- 

 Tested on the moving baTL He records observations on 

 the heat generated in water agitated by the pulping- 

 engine of a paper manufactory, and calculates the equi- 

 valent of that heat in horse-power. He compares 



the union of atoms with the union of felling 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 generated by its 

 collision would raise an equal weight of water 17,356" 

 GL in temperature. He then determines the thermal 

 fi^*riHot*oiiUbeprodK^h 7 tlKeuthiftatf&^ 

 into the sun. So that here, in 1945, we have the 

 of that meteoric theory of the sun's heat which 1 

 developed with such extraordinary ability three 

 afterwards. He also points to the almost exdnsrvi 

 cacy of the sun's heat in producing mechanics 

 upon the earth, winding up with the profound remark, 

 that the heat developed by friction in the wheels of our 

 wind and water mills comes from the sun in th<> far^a 

 of vibratory motion; while the heat produced by mills 

 driven by tidal action is generated at the expense of the 

 earth's axial rotation. 



Having thus, with firm step, passed through the 

 powers of inorganic nature, his next object is to bring 

 his principles to bear upon the phenomena of vegetable 

 and y""l life. Wood and coal ***** burn ; whenoo 



