56 POPULAR SCIENCE MONTHLY. 



The whole aim of the science is to state the phenomena of nature 

 in terms of these quantities in the most exact language possible. From 

 this point of view, a notable distinction in the kindred science of 

 chemistry is at once apparent in that whereas chemistry introduces 

 no new entity, it subdivides matter into upwards of eighty distinct ulti- 

 mates called elements, thus enormously enlarging the number of com- 

 binations and phenomena with which it must deal. 



Biology, again, while retaining all the postulates of physics and 

 chemistry, introduces a new principle, that of life, whereby the phe- 

 nomena to be treated become infinitely complex. 



If we now recall that it is only the simplest phenomena of nature 

 that can be formulated, it is at once obvious why chemistry and biology 

 are so much more backward in their growth into exact sciences, the 

 former being largely taken up with a description of the properties of 

 different substances, while the latter can do little more than group 

 together different living forms according to some principle of resem- 

 blance amid diversity. These differences make it evident that the 

 character of mind best adapted for their investigation may differ 

 somewhat in the different sciences, and also that the effects when 

 taught will be more or less diverse. Different methods of presentation 

 may likewise be found desirable. 



In physics three modes of teaching are available, each of which is 

 to be employed in conjunction with the others, each contributing an 

 indispensable, but necessarily different and unequal, portion to the 

 learner. They are (1) recitations upon a text-book, (2) demonstration 

 of phenomena in lectures, (3) work in a physical laboratory. Now 

 while there is nothing in these methods peculiar to the teaching of 

 physics, it is important to observe that not only do the function and ser- 

 vice of each method differ considerably in any one science, but that both 

 the function and service of any method are widely different in differ- 

 ent sciences. The function of the text-book is chiefly historical, i. e., 

 to record what progress in the development of the science has been 

 effected by our predecessors ; but in connection with physics it can not 

 be too strongly emphasized that the science is not a bare record of ob- 

 servations upon natural phenomena. There is nothing more character- 

 istic of the mental attitude of the physicist toward knowledge than 

 the constant desire to answer not alone the question 'how?' but 'how 

 much?' That is to say in other words, we begin to have adequate 

 knowledge of a fact only when we can measure it. 



A musician will say without hesitation that one composition is 

 more classical than another. The insufficient and essentially subjective 

 character of such knowledge is at once apparent if we press the question 

 'when is one composition twice as classical as another?' 



Physics is not a bare record of facts, but a highly developed system 



