MODERN CHEMISTRY. 443 



rapid progress it has since made. The first ten years of the 

 present century were marked by several great discoveries, 

 and by that one, signally pre-eminent above the rest, of which 

 we have largely spoken in a preceding article.* We allude 

 to what we have there called the Atomic theory ; but which 

 for our present purpose may better be termed the doctrine 

 of definite and equivalent proportions in chemical combi- 

 nation. Some idea of the importance of the principle may 

 be gained from this mere enunciation ; but its real extent 

 and value, and the place it holds among the great laws of 

 the material world, can only be understood by those well 

 instructed in physical knowledge. Of the history of the 

 discovery in its several stages, we have sufficiently spoken in 

 the article referred to. Our object is now to denote some of 

 those remarkable results which have been derived from this 

 discovery in its application to every part of chemical research 

 and philosophy. 



Chemistry we have before defined as the science which 

 regards those mutual attractions or affinities of the elemen- 

 tary molecules of matter, upon which all its laws and 

 phenomena depend; varying for each particular kind of 

 matter, simple or compound ; and varying for each in rela- 

 tion to matter of every other kind. 



It was speedily seen that the term Atom, in denoting the 

 simplest and smallest combining proportion of any body, 

 became, though not a necessary, yet a justifiable exponent 

 of the great physical principle thus developed ; and one in 

 truth which almost ceased to be hypothetical- when experi- 

 mentally applied. Scientific theories required that our con- 

 ception of the divisibility of matter should approach the 

 borders of the infinite, but rest nevertheless within the finite', 

 and all scientific research corroborates this view. The actual 



* See the preceding article in this volume, on the ' Life of Dalton. and the 

 Atomic Theory.' 



