CHAPTER XIV 



THE ATOMIC THEORY OF MATTER JOHN DALTON'S 

 LAW OF DEFINITE PROPORTIONS THE INDE- 

 STRUCTIBILITY OF THE ATOMS MOLECULAR 

 FORMATIONS CRYSTALLIZATION. 



WE have had occasion several times, in speaking 

 of the views held of the physical nature of matter 

 both by the ancient writers and among modern ones, 

 to refer to the atoms, and to the theories in which 

 they played an important part. In all of the above 

 instances they were supposed to be of one and the 

 same nature ; the use made of them required them to 

 be solid, hard, elastic and imperishable ; but nothing 

 had been shown that required these atoms of matter 

 to be essentially different one from the other, or from 

 the negative qualities that the ideas of Democritus, 

 Lucretius, or even the Aristotelian conception of the 

 Scholastics had formulated. When Boyle, and later 

 when Lavoisier, had recognized the existence of va- 

 rious elements, new ideas arose. The use of an 

 accurate balance in the examination of substances 



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