Conservation of Matter 25 



or geometrically closed boundary, is to pass 

 matter in or out through the walls. 



This law has been called the sheet-anchor 

 of chemistry, but it is very far from being 

 self-evident ; and its statement involves the 

 finding of a property of matter which 

 experimentally shall remain unchanged, 

 although nearly every other property is 

 modified. To superficial observation noth- 

 ing is easier than to destroy matter. When 

 liquid when dew, for instance evaporates, 

 it seems to disappear, and when a manu- 

 script is burnt it is certainly destroyed : but 

 it turns out that there is something which 

 may be called the vapour of water, or the 

 " matter " of the letter, which still persists, 

 though it has taken rarer form and become 

 unrecognisable. Ultimately, in order to 

 express the persistence of the permanent 

 abstraction called " matter " clearly, it is 

 necessary to speak of the " ultimate atoms " 

 of which it is composed, and to say that 

 though these may enter into various com- 

 binations, and thereby display many out- 



