ULTIMATE CONSTITUTION OF MATTER 77 



principles impressed upon them. We may look upon this 

 ancient doctrine ( which had an oriental origin long before 

 Aristotle's time) as a transcendental explanation of the 

 Nature of Matter starting from physical data. The alche- 

 mists, substituting ideas which may be called chemical, little 

 as they resemble the clear conceptions of modern chemistry, 

 assigned the differences in property of the metals to their 

 possessing the three "Chymical principles," salt, sulphur 

 and mercury, in varying degrees. Such notions seem to us 

 to be wide of the- mark ; but if we try to imagine ourselves 

 as living in the days before the principle of the Conservation 

 of Matter was determined, we shall see that the permanence 

 of Aristotle's elements could be assumed with a greater 

 show of reason than the permanence of matter. The com- 

 position of the air was known no better than the composi- 

 tion of flame. A piece of wood when ignited was converted 

 into flame save for a little residue of ash. Clearly it con- 

 sisted of ash, or earth, and flame. Boyle founded modern 

 chemistry when, in language free from ambiguity and 

 mysticism, he enunciated the theory that there are certain 

 indestructible substances which cannot be resolved into 

 simpler constitutents or transmuted one into the other. 

 Such truly unchangeable substances are properly entitled to 

 the name of "Element." 



Since they cannot be broken up into simpler bodies, the 

 chemist accepts, provisionally, the doctrine that all the 

 atoms which compose any given element are uniform in 

 shape and size, and are in every other respect of the same 

 kind. He is aware that certain elementary bodies, such as 

 carbon, boron, phosphorus, exist in more than one modifi- 

 cation or state, as different in properties as soot and 

 diamond (in the case of carbon), but for purposes of cal- 

 culation, he speaks of the atoms of each particular element 

 as if they were truly unalterable, or at any rate truly 

 indivisible. The language and formulae of chemistry imply 

 that every element has its own specific atom, which differs in 



