INTRODUCTION 



BY 



BENJAMIN HARROW 



Associate in Physiological Chemistry, 



Columbia University 



THE Greeks were the first to advance the idea that mat- 

 ter cannot be subdivided indefinitely. According to them a 

 stage would be reached beyond which no further subdi- 

 vision would be possible ; this they called the atomic stage. 



The Greek idea of atoms lay dormant until early in the 

 nineteenth century, when John Dalton revived it. In Dai- 

 ton's hands the hypothesis of atoms became the very basis 

 for building the superstructure of chemistry. 



It may be doubted whether, with the possible exception 

 of Lavoisier, any man was more responsible for laying the 

 foundations of modern physics and chemistry than Dalton, 

 native of Manchester. 



Not till the latter part of the last century did the 

 rumblings of a storm make themselves heard. Then 

 began those celebrated experiments on the electrical prop- 

 erties of gases, by J. J. Thomson and others, followed by 

 Roentgen's discovery of X-rays and Madame Curie's iso- 

 lation of radium, which opened up to view a new conti- 

 nent in science. For the gist of these achievements was 

 to show that the atom was by no means the smallest par- 

 ticle of matter ; that the atom, in fact, inconceivably small 

 though it be, was yet complex enough to resemble, in minia- 



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