THE ATOMIC VIEW OF NATURE. 



385 



About a century after the publication of the ' Principia,' 

 which, by propounding the gravitation formula, raised the 

 ancient and indefinite notion of Attraction to the rank of 

 a useful and rigorously defined expression, another favour- 

 ite theory of the ancient philosophers 1 was similarly ele- 

 vated to the rank of a leading and useful scientific idea. 



Although no mathematical relation equal in value and 2. 



Atomic 



definiteness to the gravitation formula marks the intro- the ry- 

 duction of the Atomic theory in Chemistry, it never- 

 theless owes its success to similar qualities viz., to the 

 fact that it led natural philosophers to make definite 

 measurements, and placed exact research in the place 

 of vague reasoning. 



The atomic theory, usually associated with the name 

 of Dalton, is, however, not nearly as much the historic 

 property of that great man as gravitation is that of 

 Newton, for whereas the latter gave the fullest gen- 

 eralisation that can so far be safely made, the atomic 



1 Ancient philosophers have fur- 

 nished us with three distinct ab- 

 stractions which have survived, and 

 which, put into definite mathemati- 

 cal language, have led exact research 

 in physics and chemistry in modern 

 times the theory of Attraction 

 and Repulsion, the Atomic Theory, 

 and the Kinetic Theory, or the 

 notion that everything is motion. 

 Of these three theories the second 

 was most developed in antiquity ; 

 Lucretius's great poem on the na- 

 ture of things being really a treatise 

 on the subject, in which the atomic 

 view is placed in the centre, the two 

 other ideas being likewise largely 

 utilised. The historians of ancient 

 philosophy trace these abstract or 

 leading ideas back to the earlier 

 Greek thinkers. Thus Heraclitus 



VOL. I. 



of Ephesus is credited with having 

 first taught that everything is in 

 motion. Empedocles of Agrigentum 

 made use of the notions of Attrac- 

 tion and Repulsion, poetically re- 

 presented as Love and Hatred, to 

 explain the action of his elements ; 

 and Democritus of Abdera is uni- 

 versally considered to be the true 

 founder of the atomistic theory, 

 which was adopted and developed 

 in the School of Epicurus, and very 

 fully explained by the Roman poet. 

 A very good analysis will be found 

 in Lange's ' History of Materialism ' 

 (English translation by Thomas, 3 

 vols.), in which also the historical 

 connection with modern thought, 

 especially through Bacon, Gassendi, 

 and Hobbes, is clearly brought 

 out. 



2B 



