222 WRITINGS OF JOSEPH HENRY. [1844 



phenomena of combustion the immediate source of the power 

 evolved in the form of heat, is the passage from an unstable 

 state into one of stable combination of the carbon and hy- 

 drogen of the fuel and the oxygen of the atmosphere, but 

 this power may ultimately be resolved into the force which 

 caused the separation of these elements from their previous 

 combination in the state of carbonic acid and water. 



Now the only forces of any importance which operate at 

 the surface of the earth to counteract the tendency to a gen- 

 eral state of stable equilibrium are those derived from two 

 sources, namely, celestial disturbance, and what is called vital 

 action; and hence all mechanical power, as well as all activity 

 on the surface of the globe, may be referred to these two 

 sources. The only exception to this generalization is the 

 comparatively limited effect of volcanic action, which is a 

 power, from whatever source it may be derived, that must 

 tend to exhaust itself. 



Thus far the author considered his conclusions founded 

 on well-established physical law, and perhaps here the true 

 spirit of inductive philosophy would admonish him to stop ; 

 but they who are disposed to continue the speculation, and 

 to consider the results of the late researches of the German 

 and French chemists as well-established truths, may extend 

 the generalization so as to reduce all mechanical motion on 

 the surface of the earth to a source from without. Thus, ac- 

 cording to Liebig, Dumas and Boussingault, the mechanical 

 power exerted by animals is due to the passage of organized 

 matter in the body from an unstable to a stable equilibrium ; 

 and as this matter is derived in an unstable state from vege- 

 tables, and the elements of these again from the atmosphere, 

 it would therefore appear to follow, that animal power is 

 referable to the same sources as that from the combustion of 

 fuels, namely, the original force which separates the elements 

 of the plants from their stable and original combination with 

 the oxygen of the atmosphere. But what is this power which 

 furnishes the plant with the material of its growth ? Is it 

 due to a constantly created vital power ; or since its effects 

 are never directly exhibited but in the presence of light, may 



