152 GENERAL SCIENCE 



spontaneous motion, of growth by cell division, and of repro- 

 duction. These activities are seen in plants and animals. 

 Lacking these manifestations, matter is lifeless. The bio- 

 logical sciences are those largely concerned with studies of 

 living bodies, while the physical sciences deal with the 

 phenomena of matter apart from manifestations of life in it. 

 This distinction, however, is an arbitrary one for the purpose 

 of grouping scientific knowledge into convenient fields for 

 study. In General Science no regard need be paid to these 

 distinctions. 



Whatever the changes through which matter may pass, 

 two characteristics are maintained it always occupies space, 

 and its mass (quantity of matter) remains unchanged. 

 While no one knows how matter originated, it is fully 

 believed that there is no destruction of matter in the many 

 changes to which it is subject. It is believed, too, that there 

 is no creation of any matter, though newly formed substances 

 (kinds of matter) take the places of those that have disap- 

 peared. And it is through these changes occurring in 

 matter that we learn about force. 



The study of Physics is concerned with the innumerable 

 changes occurring everywhere about us as result of so-called 

 physical forces. In these changes the nature of the matter 

 involved remains the same. Any "explanation" of these 

 changes consists very largely of statements of what these 

 results are, and what conditions affect the changes. That 

 these statements be clear and exact, it is necessary to use 

 terms with some degree of scientific accuracy. Indeed, in 

 learning the elementary and fundamental facts concerning 

 the physical forces and their phenomena 1 , there is the best of 

 opportunity to acquire accuracy of statement together with 



1 Any change in matter, however simple and familiar, is a phenomenon. 

 In popular language the use of the term often implies that which is unusual 

 and striking. 



