CHAPTER I. 



MATTER AND ENERGY. 



SECTION I. MATTER. 



WHAT is matter ? What is energy ? must of necessity be 

 the first questions asked in a survey of the sciences that deal 

 with these two subjects. A categorical answer to either 

 query is, however, an impossibility. We know matter and 

 energy only as revealed to us through their properties ; nor 

 is there any likelihood of our ever attaining to a knowledge 

 of their essential nature. In order to define the terms 

 'matter,' 'energy,' therefore, it is necessary to enumerate 

 their properties in some detail. 



Fundamental properties of matter. Matter obviously 

 exists in measurable quantities, each quantity occupying a 

 certain volume or bulk. Matter, as occupying a certain 

 volume of space, must possess appreciable length, breadth, 

 and thickness ; that is to say, each volume of matter must 

 possess a definite form. Moreover, in virtue of the universal 

 applicability of the law of gravitation viz. that every par- 

 ticle of matter in the universe attracts every other particle 

 with a force directly proportional to the mass of the attract- 

 ing particle, and inversely proportional to the square of the 

 distance between them every particle of matter must pos- 

 sess weight, that is, a tendency to rush to the centre of the 

 earth, as the nearest great attracting body. 



Matter exists in a variety of states. We are familiar 

 more especially with the solid, liquid, and gaseous states 



