PART II 



CHEMICAL THEORIES 



CHAPTER XIV 



THE ATOMIC THEORY 



A. DALTON'S ATOMIC THEORY 



Theories as to the composition of matter. From the 

 time of the Greek philosophers there had existed two 

 opposing theories of the constitution of matter (a) the 

 continuous, according to which a void could not exist, and 

 (b) the atomic, according to which all material substance 

 consisted of particles separated by spaces. 



The great English philosopher Isaac Newton gave his 

 powerful support to the latter opinion, with the result that it 

 became more and more prevalent, until at the close of the 

 eighteenth century it was almost universal to think of sub- 

 tances as composed of minute particles, too small to be 

 visible even by means of the microscope ; these tiny 

 particles were generally spoken of as " atoms," i.e. as 

 indivisible. Newton's views as to the nature of atoms are 

 set out in the following passage : 



" It seems probable to me, that God in the beginning 

 formed matter in solid, massy, hard, impenetrable, moveable 

 particles ; of such sizes and figures, and with such other 

 properties, and in such proportions to space, as most 

 conduced for the end for which he formed them ; and that 

 these primitive particles being solids, are incomparably 

 harder than any porous bodies compounded of them ; even 



2 9' U 2 



