PHYSICS 63 



then made to introduce law and order among the various 

 facts that experiment brings forth. So throughout the whole, 

 fact and phenomena are explained in terms of the funda- 

 mental principles involved. To such an extent is this suc- 

 cessful that a certain part of this branch is often referred 

 to as a case of a precise science. 



The elementary student of physics in learning the funda- 

 mental laws and definitions often fails to look beyond these 

 and discover that mechanics is a live subject; that it has a 

 great many interesting and instructive applications ; that it 

 deals not only with simple things, as the lever and the inclined 

 plane, but also with those far more complex, as the stability 

 produced in a monorail car by the action of gyroscopes. Part 

 of this subject may be called the science of machinery, for it 

 deals with the principles which involve all types of machines. 



There are many special applications, for example the so- 

 called kinetic theory of gases where, in order to be able to 

 apply these principles, it is necessary to adopt some hypothesis, 

 in this case the molecular theory of matter. These cases are 

 sometimes so involved, that it is difficult for the layman and 

 often for the student to clearly understand what is theory 

 and what is fact. But underlying all these phenomena we 

 have this precise science which we call mechanics. 



From the point of view already taken, it is obvious 

 that since mechanics treats of relations between our funda- 

 mental concepts, that is, between mass, force, motion, and 

 energy, it must be the foundation of all physics. Independ- 

 ently of this fundamental reason it was long ago found that 

 some of the other divisions of physics were special cases 

 of mechanics. For example, it was found that sound was 

 a wave motion and later that light was also a wave motion. 

 Since the study of wave motion is a sub-division of mechanics, 

 mechanics must be accepted as the more fundamental. Later 

 on, electrical waves were discovered, and it was also found 

 that some of the fundamental laws of electricity could be 



