74 o THE POPULAR SCIENCE MONTHLY. 



tluctive science with which the world has been favored since Bacon 

 promulgated his new philosophy, that the quantity of electricity con- 

 tained in a body was exactly the quantity which was necessary to 

 decompose that body. For example, in a voltaic battery of zinc and 

 copper plates a certain fixed quantity of electricity is eliminated by 

 the oxidation of a portion of the zinc. If, to produce this effect, the 

 oxygen of a given measure of water say a drop is necessary, the 

 electricity developed will be exactly that which is required to separate 

 the gaseous elements of a drop of water from each other. An equiva- 

 lent of electricity is developed by the oxidation of an equivalent of 

 zinc, and that electricity is required for the decomposition of an equiv- 

 alent of water, or the same quantity of electricity would be equal to 

 the power of effecting the recombination of oxygen and hydrogen, 

 into an equivalent of water. The law which has been so perfectly 

 established for electricity is found to be true of the other physical 

 forces. By the combustion which is a condition of oxidation of 

 an equivalent of carbon, or of any body susceptible of this change of 

 state, exact volumes of light and heat are liberated. It is theoreti- 

 cally certain that these equivalents of light and heat are exactly the 

 quantities necessary for the formation of the substance from which 

 those energies have been derived. That which takes place in terres- 

 trial phenomena is, it is highly probable, constantly taking place in 

 solar phenomena. Chemical changes, or disturbances analogous to 

 them, of vast energy, are constantly progressing in the sun, and thus 

 is maintained that unceasing outpour of sunshine which gladdens the 

 earth, and illumines all the planets of onr system. Every solar ray is 

 a bundle of powerful forces ; light, the luminous life-maintaining 

 energy, giving color to all things ; heat, the calorific power which de- 

 termines the conditions of all terrestrial matter ; actinism, peculiarly 

 the force which produces all photographic phenomena ; and electricity 

 regulating the magnetic conditions of this globe. Combined in action, 

 these solar radiations carry out the conditions necessary to animal 

 and vegetable organization, in all their varieties, and create out of a 

 chaotic mass forms of beauty rejoicing in life. 



To confine our attention to the one subject before us. Every per- 

 son knows that, to grow a tree or a shrub healthfully, it must have 

 plenty of sunshine. In the dark we may force a plant to grow, but it 

 forms no Avoody matter, it acquires no color; even in shade it grows 

 slowly and weak. In sunshine it glows with color, and its frame is 

 strengthened by the deposition of woody matter eliminated from the 

 carbonic acid of the air in which it grows. A momentary digression 

 will make one point here more clear. Men and animals live by con- 

 suming the products of the vegetable world. The process of support- 

 ing life by food is essentially one of combustion. The food is burnt 

 in the system, developing that heat which is necessary for life, and 

 the living animal rejects, with every expiration, the combinations, 



