THE ATOMIC THEOKY. 2-45 



The authority of evidence began to rephu-c the iiuthority of the 

 schools. 



Early in the seventeenth century the atomic philosoph}- of Epicurus 

 was revived by Gassendi, who was soon followed b}^ Boyle, by New- 

 ton, and by many others. One other important step was taken also. 

 Boyle, in his Sceptical Chymist, gave the first scientific definition of 

 an element, a conception which was more fully developed by Lavoisier 

 later, but which received its complete modern form onh^ after Davy 

 ha4 decomposed the alkalies and shown the true nature of chlorine. 

 Without this preliminary work of Bo3de and Lavoisier, Dalton's 

 theory would hardh^ have been possible. An elementar}' atom can be 

 given no real detinition unless we have some notion of an element to 

 begin with. But the strongest impulse came from Newton, who 

 accepted atomism in clear and unmistakable terms. 



Coming before Newton, Descartes had rejected the atomic hypothe- 

 sis, holding that there could be no vacuum in the universe and mak- 

 ing matter essentially synonymous with extension. True, Descartes, 

 in his famous theory of vortices, imagined whirling particles of 

 various degrees of fineness; but they were not atoms as atoms and 

 molecules are now conceived. It may be dangerous to pick out land- 

 marks in history and to assert that such and such a movement began 

 at such and such a time. Nevertheless, we may fairly say that the 

 turning point in physical philosophy was Newton's discovery of gravi- 

 tation, for that indicated mass as the fundamental property of matter. 

 For an}^ given portion of matter which we can segregate and identif}^ 

 extension is variable and mass is constant; when that conclusion was 

 estal)lished the dominance of atomism became inevitable. Bo3"le, 

 Newton, and Lavoisier were legitimate precursors of Dalton, but 

 whether Boscovich should be so considered is more than dou])tful. 

 His points of force were too abstract a conception to admit of direct 

 application in the solution of real problems. Dalton certainl}" owed 

 nothing to Boscovich, and would just as surely have developed his 

 theory had the brilliant Dalmatian never written a line. 



To Boyle and Newton the atomic h3^pothesis was a question of 

 natural philosoph}^ alone, for in their day chemistry as a quantita- 

 tive science had hardly begun to exist. Attempts were soon made, 

 however, to give it chemical application, and the first of these which 

 I have been able to tind was due to Emanuel Swedenborg. This phi- 

 losopher, whose reputation as a man of science has been overshadowed 

 l)y his fame as a seer and theologian, pu])lished in 1721 a pamphlet 

 upon chemistry, which is now more easily accessible in an English 

 translation of relativel}^ recent date." It consists of chapters fiom a 

 larger unpublished work, and really amounts to nothing more than a 



"Soiiu' SpeeimeiiH of a Work on the rrinciplos of Chemistry, with other Treatises. 

 London, 1847. Originally published at Amsterdam, in Latin. 



