INTRODUCTION. T 



power of one of the constituents of our atmosphere, namely, 

 oxygen. When light is unexpectedly thrown upon any pre- 

 viously obscure group of phenomena in the physical world, 

 we may the more readily believe that we are on the 

 threshold of new discoveries, when we find that these rela- 

 tions appear to be either obscure, or even in opposition to 

 already established facts. 



I have more particularly adduced examples in which the 

 dynamic actions of attracting forces seem to show the course by 

 which we may hope to approximate towards the solution of the 

 problem of the original, unchangeable, and hence named the 

 elementary heterogeneity of substances (for instance, oxygen, 

 hydrogen, sulphur, potassium, phosphorus, tin, &c.), and of the 

 amount of their tendency to combine, in other words, their che- 

 mical affinity. Differences of form and mixture are, I would 

 again repeat, the only elements of our knowledge of matter ; 

 they are the abstractions under which we endeavour to com- 

 prehend the all-moving universe, both as to its size and com- 

 position. The detonation of the fulminates under a slight 

 mechanical pressure, and the still more formidable explosion 

 of terchloride of nitrogen, which is accompanied by fire, 

 contrast with the detonating combination of chlorine and 

 hydrogen, which explodes when the sun's rays fall directly 

 upon it (more especially the violet rays). Metamorphosis, 

 union, and separation afford evidence of the eternal circu- 

 lation of the elements in inorganic nature no less than in 

 the living cells of plants and animals. "The quantity of 

 existing matter remains however the same, the elements 

 alone change their relative positions to one another." 



We thus find a verification of the ancient axiom of 

 Anaxagoras, that created things neither increase nor de- 

 crease in the Universe, and that that which the Greeks 

 termed the destruction of matter was a mere separation of 

 parts. Our earthly sphere, within which is comprised all 

 that portion of the organic physical world, which is accessible 

 to our observation, is apparently a laboratory of death and 

 decay ; but that great natural process of slow combustion, 

 which we call decay, does not terminate in annihilation. The 

 liberated bodies combine to form other structures, and through 

 the agency of the active forces which are incorporated ill 

 them a new life germinates from the bosom of the earth. 



