MATTEE AND FOKCE. 61 



lines, called, by some, ' magnetic curves,' and, by 

 others, ' lines of magnetic force.' Over two magnets 

 now before me is spread a sheet of paper. Scattering 

 iron filings over the paper, polar force comes into play, 

 and every particle of the iron responds to that force. 

 \Ye have a kind of architectural effort if I may use 

 the term exerted on the part of the iron filings. Here 

 then is a fact of experience which, as you will see 

 immediately, furnishes further material for the mind to 

 operate upon, rendering it possible to attain intellectual 

 clearness and repose, while speculating upon apparently 

 remote phenomena. 



The magnetic force has here acted upon particles 

 visible to the eye. But, as already stated, there are 

 numerous processes in nature which entirely elude the 

 eye of the body, and must be figured by the eye of the 

 mind. The processes of chemistry are examples of these. 

 Long thinking and experimenting has led philosophers 

 to conclude that matter is composed of atoms from 

 which, whether separate or in combination, the whole 

 material world is built up. The air we breathe, for ex- 

 ample, is mainly a mechanical mixture of the atoms 

 of oxygen and nitrogen. The water we drink is also 

 composed of oxygen and hydrogen. But it differs 

 from the air in this particular, that in water the 

 oxygen and hydrogen are not mechanically mixed, 

 but chemically combined. The atoms of oxygen and 

 those of hydrogen exert enormous attractions on each 

 other, so that when brought into sufficient proximity 

 they rush together with an almost incredible force to 

 form a chemical compound. But powerful as is the 

 force with which these atoms lock themselves together, 

 we have the means of tearing them asunder, and the 

 agent by which we accomplish this may here receive a 

 few moments' attention* 



