THE SIZE OF ATOMS. 149 



view that matter, although we may conceive it 

 to be infinitely divisible, is not infinitely divisible 

 without decomposition. Just as a building of 

 brick may be divided into parts, into a part 

 containing 1000 bricks, and another part con- 

 taining 2500 bricks, and those parts viewed 

 largely may be said to be similar or homoge- 

 neous ; but if you divide the matter of a brick 

 building into spaces of nine inches thick, and 

 then think of subdividing it farther, you find 

 you have come to something which is atomic, 

 that is, indivisible without destroying the elements 

 of the structure. The question of the molecular 

 structure of a building does not necessarily 

 involve the questions, Can a brick be divided 

 into parts ? and Can those parts be divided into 

 much smaller parts ? and so on. It used to be 

 a favourite subject for metaphysical argument 

 amongst the schoolmen whether matter is in- 

 finitely divisible, or whether space is infinitely 

 divisible, which some maintained ; whilst others 

 maintained that matter only is not infinitely 

 divisible, and demonstrated that there is nothing 



