MONISM AND DUALISM 227 



is made, and energy as the power which moves mat- 

 ter. The two are always found in association ; and, 

 as Newton said, force is inherent in matter. 

 Matter we divide into the imponderable sother which 

 fills space, and ordinary matter which is subject to 

 the law of gravitation. Of the sether we know 

 nothing, because it evades our senses altogether; 

 and we believe in its existence only because it is 

 impossible to explain radiant energy, traversing 

 inter-stellar space, without it. Ponderable matter 

 is supposed to be made up either of minute, solid, 

 hard bodies of different specific weights and with 

 different affinities, called atoms; or else of vortex- 

 rings of ffither, that is of portions of aether in rapid 

 circular or spiral movement. 



The atomic hypothesis accounts for the indestruc- 

 tibility and impermeability of matter, as well as for 

 inertia and chemical affinity. Its chief difficulty is 

 that gases behave as if they were composed of 

 spherical bodies which are perfectly elastic; while, 

 if an atom was solid, hard and indivisible, its sur- 

 face could not be indented by the impact of another 

 atom, and there could be no rebound. Secchi pro- 

 posed to get over this difficulty by the supposition 

 that atoms were always combined into rotating 

 groups. But it is very doubtful whether such rota- 

 ting groups could retain their movements indefinitely 

 among the incessant shocks to which they are ex- 

 posed. Of late years many physicists have come to 

 the conclusion that atoms are built up from 

 numerous ions of two kinds, positive and negative. 

 And probably, when we know the difference between 



