THE ETHER AND PONDERABLE MATTER 



in 



Quite aside from the question of the exact constitu- 

 tion of the ultimate particles of matter, questions as to 

 the distribution of such particles, their mutual relations, 

 properties, and actions, have come in for a full share of 

 attention during our century, though the foundations 

 for the modern speculations were furnished in a pre- 

 vious epoch. The most popular eighteenth -century 

 speculation as to the ultimate constitution of matter 

 was that of the learned Italian priest, Eoger Joseph 

 Boscovich, published in 1758, in his Theoria Philoso- 

 phic Naturalis. " In this theory," according to an 

 early commentator, " the whole mass of which the 

 bodies of the universe are composed is supposed to con- 

 sist of an exceedingly great yet finite number of simple, 

 indivisible, inextended atoms. These atoms are endued 

 by the Creator with repulsive and attractive forces, 

 which vary according to the distance. At very small 

 distances the particles of matter repel each other ; and 

 this repulsive force increases beyond all limits as the 

 distances are diminished, and will consequently forever 

 prevent actual contact. When the particles of matter 

 are removed to sensible distances, the repulsive is ex- 

 changed for an attractive force, which decreases in in- 

 verse ratio with the squares of the distances, and extends 

 beyond the spheres of the most remote comets." 



This conception of the atom as a mere centre of force 

 was hardly such as could satisfy any mind other than 

 the metaphysical. No one made a conspicuous attempt 

 to improve upon the idea, however, till just at the close 

 of the century, when Humphry Davy was led, in the 

 course of his studies of heat, to speculate as to the 

 Q 241 



