52 POPULAR SCIENCE MONTHLY. 



ON THE STUDY OF PHYSICS. 



By Professor FREDERICK E. BEACH, 



YALE UNIVERSITY. 



THE domain of physics is coextensive with the whole range of 

 phenomena of the material world, but the science of physics, 

 as commonly understood, is restricted to a much smaller field whose 

 boundaries were perhaps first marked by setting off certain groups of 

 phenomena for special study. 



In this way there arose five significant branches of physical science : 

 ( 1 ) Astronomy, in which are treated the facts and phenomena observed 

 in connection with the heavenly bodies. One peculiarity of astronom- 

 ical phenomena is worth noting, namely, that they are entirely beyond 

 human control and can not be made the subject of experiment. (2) 

 Chemistry, which treats the relations of different kinds of matter one 

 to another, and those phenomena which accompany material changes, 

 i. e., alteration in the composition of substances. (3) Biology, which 

 deals with vital phenomena; current, as in physiology, or past, as in 

 paleontology. (4) Meteorology, in which are grouped phenomena 

 peculiar to the earth's atmosphere and incapable of repetition at will. 

 (5) All the remaining natural phenomena form the subject of physics, 

 which may be said to treat of mechanics, i. e., the motion and inter- 

 action of bodies upon one another, and of those groups of phenomena 

 commonly designated as heat, light, sound and electricity. These 

 conventional divisions of science involve other differences not always 

 clearly apprehended, but important alike to the student and the teacher. 



While one may not say that one branch of knowledge is more worthy 

 than another, one set of facts may be more precise or scientific than 

 another, whatever may be the meaning attached to the word. Exactly 

 where to draw the line between science and knowledge has been the 

 subject of some dispute. For the purpose of the present discussion we 

 will adopt as the definition of a science, the precise knowledge of a 

 body of facts accurately verified and erected into a logical system. In 

 this definition, only those branches of learning are intentionally excluded 

 from the rank of science in which the knowledge is either ill defined, or 

 uncertain, or unsystematized, though just what classes of historical in- 

 vestigation or of psychological speculation fail to meet the requirement 

 are of no moment, as we are at present concerned only with branches 

 of physical science. It is obvious that the branches of science thus 

 defined may differ considerably in the precision with which the facts 



