VITALITY SS 



whilom molten condition of our planet was, as supposed 

 bj eminent men, due to the collision of cosmic masses or 

 not, it is perfectly certain that the molten condition might 

 be thus brought about. If, then, solar light and heat can 

 be produced by the impact of dead matter, and if from 

 the light and heat thus produced we can derive the ener- 

 gies which we have been accustomed to call vital, it indu- 

 bitably follows that vital energy may have a proximately 

 mechanical origin. 



In what sense, then, is the sun to be regarded as the 

 origin of the energy derivable from plants and animals ? 

 Let us try to give an intelligible answer to this question. 

 Water may be raised from the sea-level to a high eleva- 

 tion, and then permitted to descend. In descending it 

 may be made to assume various forms — to fall in cas- 

 cades, to spurt in fountains, to boil in eddies, or to flow 

 tranquilly along a uniform bed. It may, moreover, be 

 caused to set complex machinery in motion, to turn mill- 

 stones, throw shuttles, work saws and hammers, and 

 drive piles. But every form of power here indicated 

 would be derived from the original power expended in 

 raising the water to the height from which it fell. There 

 is no energy generated by the machinery: the work per- 

 formed by the water in descending is merely the parcel- 

 ling out and distribution of the work expended in raising 

 it. In precisely this sense is all the energy of plants and 

 animals the parcelling out and distribution of a power 

 originally exerted by the sun. In th« case of the water, 

 the source of the power consists in the forcible separation 

 of a quantity of the liquid from a low level of the earth's 

 surface, and its elevation to a higher position, the power 

 thus expended being returned by the water in its descent. 



