458 WRITINGS OF JOSEPH HENRY. [1866 



the relative ecouomy in the expenditure of a definite amount 

 of food in the natural machine and the artificial engine. 

 The former has been found to wasteless of the motive power 

 than the latter. 



In pursuing this train of investigation the question is 

 asked, " Whence does the coal or food derive its power ?" 

 The answer is, that these substances are derived from the 

 air by the decomposing agency of the impulses from the sun, 

 and that when burned in the engine or consumed in the 

 body they are again resolved into air, giving out in this 

 resolution an amount of energy equivalent to that received 

 from the sun during the process of their growth. All the 

 materials of the crust of the earth, with the exception of coal 

 and organic matter, are in a state of inertness, and like the 

 burnt slag of the furnace, have expended their energy, and 

 in this condition of inertness the}'^ would forever remain, 

 were it not for extraneous influences, principally that from 

 the sun. 



From this point of view the phenomena we have been 

 considering consist merely in the transfer of power from one 

 body to another, and from a wide generalization from all 

 the facts, the conclusion has been arrived at that energy is 

 neither lost nor gained in the transfer; and pursuing the 

 same train of reflection, we are finally led to the result that 

 all power is derived from the primordial, unbalanced attrac- 

 tion and repulsion of the atoms of matter. 



In the gradual development of the principles we have 

 given there has been a tendency to extend the views we 

 have presented too far, and to refer all the phenomena of life 

 to the mechanical or chemical forces of nature. Although 

 it has been, as we think, conclusively proved that from food, 

 and food alone, come all the different kinds of physical force 

 which are manifest in animal life, yet as the author of the 

 preceding paper has shown, there is something else neces- 

 sary to life, and this something, though it cannot properly 

 be called a force, may be denominated the vital principle. 

 Without the influence of this principle the undirected physi- 

 cal powers produce mechanical arrangements and assume a 



