8 WRITINGS OF JOSEPH HENRY. [1855- 



No truth is more important in regard to the material well- 

 being of man, and none requires to be more frequently en- 

 forced upon the public mind, than that the improvement 

 and perfection of art depends upon the advance of science. 

 Although many processes have been discovered by accident, 

 and practiced from age to age without a knowledge of the 

 principles on which they depend, yet as a general rule such 

 processes are imperfect, and remain, like Chinese art, for 

 centuries unchanged or unimproved. They are generally 

 wasteful in labor and material, and involve operations Mdiich 

 are not merely unessential, but actually detrimental. The 

 dependence of the improvement of agriculture upon the ad- 

 vance of general science, and its intimate connection with 

 meteorology in particular, must be evident when we reflect 

 that it is the art of applying the forces of nature to increase 

 and improve those portions of her productions which are 

 essential to the necessity and comfort of the human race. 



Modern science has established, by a wide and careful in- 

 duction, the fact that plants and animals consist principally 

 of solidified air, the only portions of an earthy character 

 which enter into their composition being the ashes that re- 

 main after combustion. All the other parts were origi- 

 nally in the atmosphere, were absorbed from the mass of air 

 during the growth of the plant or animal, and are given 

 back again to the same fountain from which they were drawn, 

 in the decay of the vegetable, and in the breathing and 

 death of the animal. 



The air consists of oxygen, nitrogen, carbonic acid, the 

 vapor of water, traces of ammonia, and of nitric acid. A 

 young plant placed in the free atmosphere and exposed to 

 the light of the sun, gradually increases in size and weight 

 by constantly receiving carbon from the carbonic acid of the 

 air, which being thus decomposed, evolves the liberated oxy- 

 gen. The power by which this decomposition is produced 

 is now known to be due to the solar ray, which consists of a 

 peculiar impulse or vibration, propagated from the distant 

 sun, through a medium filling all space. 



It is a principle of nature that power is always absorbed 



