SCIENCE 



NEW YORK, APRIL 21, 1893. 



LABORATORY INSTRUCTION IN PHYSICS. 



BY D. W. BERING, UNIVERSITT OP THE CITY OF NEW YORK. 



There are various practices, and seemingly but two clearly de- 

 fined methods of teaching physics in college laboratories. The 

 first method, which may be called the progressive one, treats the 

 general subject of physics by going through its various divisions 

 successively, until the whole ground has been covered, whether 

 tboroughly or superficially. For students who have had no pre- 

 liminary training in physics, this method is the only practicable 

 one if they are to begin their study in the laboratory. The other 

 may be called the method of analysis. It assumes that the pupil 

 has received a fair course of instruction in the principles of the 

 science before he enters upon laboratory work. Then it is a 

 matter of indifference whether his first exercise is one in optics, 

 or in electricity ; in radiation, or in specific gravities. He will 

 examine a body of any sort with reference to its various proper- 

 ties, taking account of as many as he can, which in some in- 

 stances may embrace nearly the whole range of physics. This 

 method then does not present the different features of physics 

 so much as the physical features of different things. 



At first sight it would appear as if the method that is pursued for 

 the direct purpose of learning the science would be the one best 

 fitted to give an acquaintance with it, and perhaps this would be 

 true if sufficient time could be given to it to deal with the vari- 

 ous branches of physics with tolerable thoroughness, but labora- 

 tory work by an untrained pupil is slow at best, and time is lim- 

 ited. It is important, therefore, to follow the plan that willgive 

 good results without loss of time. 



If physics as a science were distinctly progressive in its nature, 

 one step being essential to a comprehension of the next, and 

 therefore of necessity a preliminary to it, there could be no 

 question as to the best order of proceeding in teaching or in 

 learning the subject. There would still be room for question as 

 to how much should be done by the teacher in experimental il- 

 lustration with discussions, before putting the pupil to experi- 

 menting on his own account, but the order of dealing with the 

 subject in any case would be determined beforehand. But it is 

 thus progressive to only a limited degree. Except for the prin- 

 ciples of mechanics, which permeate the entire science, physics, 

 in all its diversity, may be dealt with regardless of the order in 

 wbich the subjects are taken up And this exception is not 

 always recognized. Among recent standard text-bools which 

 are meant to be especially adapted to laboratory practice, but 

 which mean to omit none of the elementary principles of physics, 

 there is every variety in arrangement of topics. One begins 

 with specific gravity and air pressure, follows with dynamical 

 principles, and presents light as the final subject. Another 

 begins with magnetism, introduces the last third of the work by 

 dynamics, and closes with sound. Still another begins with 

 properties of matter and dynamics and ends with light; while a 

 fourth begins with the mechanical powers and closes with mag- 

 netism and electricity. Even the special divisions, as electrici- 

 ty, for example, can scarcely be said to be developed from one 

 principle that necessarily comes first, to another that can be 

 reached only at the end of a well-defined series. Some classifi- 

 cation of topics can always be made, but the tendency to-day is 

 to diminish rather than increase the number of classes. Con- 

 siderations of intrinsic difficulty, or length of time that can be 

 given without interruption, or the season of the year when sunny 

 days may be expected, or other special points may lead to a 

 preference as to the order of subjects, but there is little in the 

 nature of the subjects themselves to determine it. 



The status of the student when he is to enter upon the work 

 which this paper is to discuss, will depend upon the manner in 

 which he obtained his first training in physics. He may have 

 acquired his early knowledge by experimentation from the begin- 

 ning, or he may have been taught from descriptive text-books 

 supplemented by experimental lectures from the teacher, or he 

 may have had a combination of both. In the first case, he had 

 to find out principles and laws as well as (to him) disconnected 

 facts by his own experimentation; in the second, he has been 

 made acquainted with the leading laws and properties and per- 

 haps has had some opportunity to verify and apply them. 

 Whether an attempt to learn physics from the beginning by 

 practice is profitable or advisable has been much discussed, and 

 it is outside of our purpose to enter upon that question. It is a 

 plan that has grown in favor greatly of late, and has been insist- 

 ed upon by Harvard College, as a preparation for those who are 

 to pursue the subject in college. Let us suppose the pupil to 

 have acquired a general, though elementary, acquaintance with 

 the principles of the science,— that he has reached the standard 

 of at least a well-prepared college junior. For this he has prob- 

 ably been called upon to cover the whole range of the subject 

 whether by experiment, or by recitations and experimental lect- 

 ures. The advocates of the two methods of preparation will 

 find points to offset one another in the results attained. The 

 experimental student will have acquired his knowledge in a very 

 valuable way, by objective study, by the inductive method. He 

 will have " learned to do by doing." This has become a favor- 

 ite idea with educators in almost every branch of learning, and 

 its advantages are undeniable in most lines of work, but they are 

 not equally great or equally obvious in all branches or at all 

 stages. It is a most effective way so far as it goes, but in phy- 

 sics the experiments concerning any one point, or involving any 

 law, will have been so small in number under the best opportuni- 

 ties, that the student must infer the law from instances altogeth- 

 er too few and too little varied, to justify an inference. Potent 

 as the inductive method has been in science, its demonstrations 

 are never incontestable, they never rise above a moral certainty, 

 and do not even approach it, if the instances upon which the con- 

 clusions are based are not numerous, or else very accurate. The 

 student will in reality have done nothing more than illustrate a 

 point, doing in a crude way what the lecturer before a large 

 class does in a better way. Still the experiment and its results 

 will impress themselves upon him because he did the work him- 

 self. In this he will have the advantage of the lecture-taught 

 student. The knowledge of the latter, however, is likely to be 

 more correct as to principles. On the whole, the two classes may 

 be said to approach the higher laboratory practice about equally 

 well equipped : the former better prepared for manipulation 

 with perhaps less readiness to appreciate the science; the latter 

 better prepared to discriminate as to principles, but less expert 

 in determining them. Didactic and experimental instruction 

 are now so well combined in some secondary schools as to make 

 their work superior to that offered in many colleges. Having 

 been fairly well taught by any method, we may suppose the 

 student ready for practical work somewhat more advanced than 

 is to be had in secondary schools, or even in the general course 

 of physics in an average American college. What plan shall be 

 followed in his laboratory work? Presumably that plan is best 

 which is best fitted to accomplish its purpose. What is the pur- 

 pose of his work? Usually not independent research or original 

 investigation. Work of that class is generally undertaken only 

 by graduates or special students, who are not obliged to accom- 

 plish a definite amount in a given time. The higher laboratory 

 work of the college undergraduate is for the purpose of making 

 him practically familiar with physical laws, not in one particular 



