378 FRAGMENTS OF SCIENCE. 



position it lies always to the east of the moon's 

 meridian. The waters of the ocean are in part dragged 

 as a brake along the surface of the earth ; and as a 

 brake they must diminish the velocity of the earth's 

 rotation. 1 Supposing then that we turn a mill by the 

 action of the tide, and produce heat by the friction 

 of the millstones ; that heat has an origin totally dif- 

 ferent from the heat produced by another mill which 

 is turned by a mountain stream. The former is pro- 

 duced at the expense of the earth's rotation, the latter 

 at the expense of the sun's radiation. 



The sun, by the act of vaporisation, lifts mechani- 

 cally all the moisture of our air, which when it con- 

 denses falls in the form of rain, and when it freezes falls 

 as snow. In this solid form it is piled upon the Alpine 

 heights, and furnishes materials for glaciers. But the 

 sun again interposes, liberates the solidified liquid, and 

 permits it to roll by gravity to the sea. The me- 

 chanical force of every river in the world as it rolls 

 towards the ocean, is drawn from the heat of the sun. 

 No streamlet glides to a lower level without having 

 been first lifted to the elevation from which it springs 

 by the power of the sun. The energy of winds is also 

 due entirely to the same power. 



But there is still another work which the sun per- 

 forms, and its connection with which is not so obvious. 

 Trees and vegetables grow upon the earth, and when 

 burned they give rise to heat, and hence to mechanical 

 energy. Whence is this power derived ? You see this 

 oxide of iron, produced by the falling together of the 

 atoms of iron and oxygen ; you cannot see this trans- 

 parent carbonic acid gas, formed by the falling together 



1 Kaat surmised an action of this kind. 



