58 POPULAR SCIENCE MONTHLY. 



and must be studied by the individual in the laboratory. In any 

 elementary course they are relatively few in number, and even in a 

 fully equipped laboratory are rarely shown to any but the most ad- 

 vanced students. 



The value of the lecture demonstrations must again be emphasized 

 in connection with the fact that a number of the most important phe- 

 nomena, such, for example, as those of electricity, make no direct 

 or at least no unmistakable appeal to our senses, and are apprehended 

 only by some very ordinary occurrence like the movement of two objects 

 in the field of vision. For example, a discovery of such immense impor- 

 tance as that of current induction by Faraday was evidenced to him 

 only by the minute and momentary motion of a needle over a scale. 

 And since throughout the whole range of physics the measurements are 

 rarely direct, so that the interpretation of the reading of any apparatus 

 is of more importance than making the reading, the first introduction 

 to physical apparatus may often better be given on the lecture table 

 than in the laboratory. 



In turn with this brief discussion of the use of the text-book and 

 the lecture demonstration the peculiar function of the physical labora- 

 tory deserves careful examination. We remark first of all that because 

 experimental examination and dissection are essential to the teach- 

 ing of biology it does not therefore follow that the laboratory teaching 

 of physics is essential; nor because laboratory manipulation and ob- 

 servation are necessary to the teaching of chemistry does it follow that 

 laboratory manipulation and observation must be necessary and indis- 

 pensable to the teaching of physics. In such a statement there is not, 

 however, intended the faintest suggestion that work in the physical 

 laboratory is anything but useful and necessary, but rather to em- 

 phasize how widely the function of the physical laboratory differs from 

 that of the chemical and biological laboratories. Physics is an exact 

 science (though just what that means can be learned only in a physical 

 laboratory) while biology is not so at all and chemistry is but to a 

 limited degree. 



Biology may be said to have formulated a few general laws, such, 

 for example, as the law of biogenesis or the doctrine that life is gener- 

 ated by living beings only ; the law of natural selection or the doctrine 

 that the structure and function of any organism are the results of 

 the survival of those members of a class which were best fitted to their 

 surroundings ; the law of prepotency which asserts that the probability 

 of any organism approximating to its type increases with the number 

 of its ancestors of that type. None of these laws contain any quantita- 

 tive elements and consequently are never made the subject of laboratory 

 measurements. As the rest of the science is for the most part a system 

 of more or less rational classification of multitudinous forms of life, 



