DIVISIBILITY OF MATTER ATOMIC THEORY. 69 



The experiments of Karsten and Grove in fixing on a 

 plate of glass the image of a coin simply laid upon it 

 and electrified, shows, as do the phenomena in photo- 

 graphy, the exquisitely minute changes which molecules 

 undergo in ways utterly inappreciable by human sense 

 or conception. 



In subjects of this kind one question follows 

 another by instant suggestion. It may be, and has 

 been asked, is matter in any of its forms, from the in- 

 visible atom to the great globes of heaven, ever really 

 at rest ? Is not mobility, as an inherent property and 

 function of matter, actually expressed by the unceasing 

 motion of its parts, whatever their mode of aggrega- 

 tion ? Astronomy would seem to answer in the affirm- 

 ative for all that belongs to its vast domain. Organic 

 life, in its every shape on earth, tells the same story of 

 unceasing motion and change in the atomic elements 

 on which life depends. Inorganic substances do not 

 afford the same direct evidence. Yet if that be, as 

 now commonly supposed, a simple induced condition of 

 atomic motions in bodies, such motion, in one degree 

 or other, must ever be present in all matter, altered 

 more or less whenever bodies of unequal temperature 

 come into proximity. The doctrine of latent heat some- 

 what obscures this conception ; but the doctrine and 

 phrase are provisional only for the expression of a very 

 obscure physical fact. In gases more especially we 

 obtain strong presumption of incessant movement in 

 the atoms composing them. Eecent researches on their 

 interdiffusion and subjection to pressure go far to 

 justify this belief one subject, however, to those ele- 



