BOOK TWO. 

 MATTER AND ENERGY. 



CHAPTER IV. 

 A CENTURY OF CHEMISTRY. 



SEARCH FOE THE ELEMENTS. 



Different Kinds of Things. An inquisitive out- 

 look on the world at once gives us the impression of 

 an enormous number of different kinds of things 

 different in substance or composition as well as in 

 form and activity and we feel the need of arranging 

 these in some order. 



If we continue our inquisitive outlook we soon per- 

 ceive that no small part of the apparent variety of 

 the things we see around us is due to the fact that 

 different stuffs or kinds of matter occur mixed up 

 together. If we take a handful of coarse sand from 

 the shore, we can, by working for a few hours, put 

 it into some order, placing fragments of lime shells 

 in one corner and pieces of quartz in another, and so 

 on. But this sorting out is easy work, and can be 

 done by a machine; it is not the chemist's problem, 

 he deals with the changes in the nature of substances 

 which are not mixtures. Among these not-mixtures 

 it is necessary to distinguish (1) a certain number of 

 definite kinds of matter which cannot be separated by 

 any known means into unlike parts, such as iron and 



