INTRODUCTORY LECTURE ON EXPERIMENTAL PHYSICS. 243 



The simpler the materials of an illustrative experiment, and the more familiar 

 they are to the student, the more thoroughly is he likely to acquire the idea 

 which it is meant to illustrate. The educational value of such experiments is 

 often inversely proportional to the complexity of the apparatus. The student 

 who uses home-made apparatus, which is always going wrong, often learns more 

 than one who has the use of carefully adjusted instruments, to which he is apt 

 to trust, and which he dares not take to pieces. 



It is very necessary that those who are trying to learn from books the 

 facts of physical science should be enabled by the help of a few illustrative 

 experiments to recognise these facts when they meet with them out of doors. 

 Science appears to us with a very different aspect after we have found out 

 that it is not in lecture rooms only, and by means of the electric light pro- 

 jected on a screen, that we may witness physical phenomena, but that we may 

 find illustrations of the highest doctrines of science in games and gymnastics, 

 in travelling by land and by water, in storms of the air and of the sea, and 

 wherever there is matter in motion. 



This habit of recognising principles amid the endless variety of their action 

 can never degrade our sense of the sublimity of nature, or mar our enjoyment 

 of its beauty. On the contrary, it tends to rescue our scientific ideas from 

 that vague condition in which we too often leave them, buried among the 

 other products of a lazy credulity, and to raise them into their proper position 

 among the doctrines in which our faith is so assured, that we are ready at all 

 times to act on them. 



Experiments of illustration may be of very different kinds. Some may be 

 adaptations of the commonest operations of ordinary life, others may be carefully 

 arranged exhibitions of some phenomenon which occurs only under peculiar 

 conditions. They all, however, agree in this, that their aim is to present some 

 phenomenon to the senses of the student in such a way that he may associate 

 with it the appropriate scientific idea. When he has grasped this idea, the 

 experiment which illustrates it has served its purpose. 



In an experiment of research, on the other hand, this is not the principal 

 aim. It is true that an experiment, in which the principal aim is to see what 

 happens under certain conditions, may be regarded as an experiment of research 

 by those who are not yet familiar with the result, but in experimental 

 researches, strictly so called, the ultimate object is to measure something which 

 we have already seen to obtain a numerical estimate of some magnitude. 



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