-1859] WRITINGS OF JOSEPH HENRY. 9 



in producing a change in matter. This change may be per- 

 manent, or it may be of such a character as to re-produce the 

 power which was expended in effecting it. For example, 

 the moving power of a cannon ball is permanently expended 

 in passing into the side of a ship; but if the same ball were 

 shot into the mouth of another cannon, and made to com- 

 press a spring, the recoiling of the latter would give to the 

 ball, in an opposite direction, precisely the same velocity 

 which it had expended in compressing the spring, suppos- 

 ing nothing lost by friction, &c. This example serves to 

 illustrate the effect of the impulse from the sun. It decom- 

 poses the carbonic acid which surrounds the leaf of the 

 plant, or in other words, overcomes the natural attraction 

 between the carbon and the oxygen of which the acid is 

 composed, and in this effort the motions of the atoms of the 

 setherial medium are themselves stopped. The power how- 

 ever in this case is not permanently neutralized, for when 

 the plant is consumed, either by rapid combustion or by 

 slow decay, — that is, when the carbon and the oxygen are 

 again suffered to rush into union to form carbonic acid, — the 

 same amount of power is evolved in the form of light, heat, 

 or nervous force which was absorbed in the original compo- 

 sition. If the plant moreover be consumed in the animal, 

 the same power is expended in building up the organiza- 

 tion, in producing locomotion, and the incessant action of 

 the heart, and the other involuntary movements necessary 

 to the vital process. 



Plants are therefore the recipients of the power of the sun- 

 beam. They transfer this power to the animal, and the 

 animal again returns it to celestial space, whence it ema- 

 nated. To properly so direct this power of the sun-beam 

 that no part of it may run to waste, or be unproductive of 

 economical results, it is essential that we know something 

 of its nature; and the lifetime of labor of many individuals, 

 supported at public expense, would be well applied in ex- 

 clusive devotion to this one subject. The researches which 

 have been made in regard to it have developed the fact that 

 the impulses from the sun are of at least four different char- 



