SOURCES OF TERRESTRIAL ENERGY 



formation of solar radiance. These must be de- 

 scribed with somewhat more of detail. First, 

 with the exception of the changes wrought by 

 the tides, all the geologic phenomena classed as 

 aqueous are manifestations of transformed solar 

 energy. Pulses of molecular motion proceed- 

 ing from the sun are stored as reserved energy 

 in masses of aqueous vapour raised from the sea. 

 This energy is again partly given out as the 

 vapour is condensed into rain and falls to the 

 ground. The portion which remains is expended 

 in the transfer of the fallen water through the 

 soil, till it collects in rivulets, brooks, and rivers, 

 and gradually descends to the ocean whence so- 

 lar radiance raised it, bearing along with it divers 

 solid particles which go to form sedimentary 

 strata. The wind which blew these clouds into 

 the colder regions where they consolidated into 

 raindrops, was set in motion by solar energy, 

 — since all winds are caused by the unequal 

 heating of different parts of the earth's surface. 

 Molar motion stored up in these vast masses 

 of moving air is given out not only in the driv- 

 ing of clouds, but also in the raising of waves 

 on rivers and oceans ; and it is still further ex- 

 pended in the wearing away of shores and in- 

 dentation of coast-lines which these waves effect. 

 All the energy thus manifested by rains and rivers, 

 winds and waves, is transformed solar radiance. 

 And in like manner, if asked whence came the 

 327 



