CONSTITUTION OF MATTER. 23 



CHAPTER II. 



CONSTITUTION OF MATTER. 



[Note to the Teacher. In pursuing a logical arrangement of matter, the 

 principles of chemical philosophy appropriately precede the descriptive por- 

 tion of chemistry, and yet to some minds abstract ideas are exceedingly 

 difficult of comprehension, and can best be grasped after having acquired 

 a number of facts and phenomena with which to connect them. It is hard- 

 ly to be expected, then, that all young pupils will be able to intelligently 

 learn many parts of this and the two succeeding chapters ; it is recommend- 

 ed, therefore, that these chapters be carefully reviewed after having com- 

 pleted the study of the first ten chapters. Nomenclature and notation 

 should, however, be dwelt upon on the first perusal until the pupil is per- 

 fectly familiar with the systems employed. EDITOR.] 



19. Constitution of Matter. You have already learned in 

 Part I, p. 17, that matter is in the abstract any thing which 

 is perceptible by the senses, but that we do not know any 

 thing of its nature ; we can only observe its phenomena and 

 learn its properties. In order to interpret facts and to aid in 

 their classification, theories have been formed regarding the 

 nature of matter, and one of these is of importance to us. 

 Theories, you should bear in mind, are not to be considered 

 as having the same weight of authority as facts, but as mere 

 matters of convenience, which are liable to be supplanted 

 by other and new theories so soon as the old ones prove in- 

 sufficient. We do not propose to trouble you with meta- 

 physical speculations, but will explain the so-called atomic 

 philosophy simply and briefly, both because it is interesting 

 and apparently true, and also because its consideration will 



