June 18, 1909] 



SCIENCE 



961 



in the second and third years of our high 

 schools. The book has been received with 

 great approbation by the German teachers. 

 Thus although we are ahead of our col- 

 leagues across the water in the matter of 

 laboratory equipment, they are, in my 

 opinion, far ahead of us in their knowledge 

 and practise of sound pedagogy. 



The essential distinction that I have been 

 endeavoring to make plain between vigor 

 and rigor, between intuition and logic, be- 

 tween concrete and abstract, between rela- 

 tive and absolute, between interest with 

 true discipline and duty with martial rule, 

 has been pointed out for mechanics most 

 clearly by Professor Henri Poincare in his 

 "Science and Hypothesis,"* as follows: 



The principles of mechanics, then, present them- 

 selves to us under two different aspects. On the 

 one hand, they are truths founded on experiment 

 and approximately verified so far as concerns 

 almost isolated systems. On the other hand, they 

 are postulates applicable to the totality of the 

 universe and regarded as rigorously true. If 

 these postulates possess a generality and a cer- 

 tainty which are lacking to the experimental 

 verities whence they are drawn, this is because 

 they reduce in the last analysis to a mere conven- 

 tion which we have the right to make, because we 

 are certain beforehand that no experiment can 

 contradict it. This convention, however, is not 

 absolutely arbitrary; it does not spring from our 

 caprice; we adopt it because certain experiments 

 have shown us that it would be convenient. Thus 

 is explained how experiment can make the prin- 

 ciples of mechanics, and yet why it can not over- 

 turn them. 



Hence the particular part of the physics 

 teacher's problem now before us reduces to 

 this: The present system of teaching phys- 

 ics in its elementary stages fails because 

 of its leaning toward rigor, logic, the ab- 

 stract, the absolute and martial law: the 

 problem is to change the methods of teach- 

 ing so that vigor, intuition, the concrete, 

 the relative and true discipline shall pre- 

 vail. One suggestion has already been 

 made as to ways of doing this, namely, 



* English translation, p. 98. 



omit the absolute units. In closing let me 

 throw out two further hints that may assist 

 those who wish to take part in the house- 

 cleaning that is at hand. 



Physics is suffering from lack of unity 

 in the way it is presented to beginners. 

 This may be remedied by a suitable use of 

 the idea of energy. In a recent address at 

 the University of Chicago, Professor G. H. 

 Mead showed that the doctrine of energy 

 plays in physical science the same role as 

 does the doctrine of evolution in biological 

 science, since it furnishes concepts and a 

 terminology in which all forms of physical 

 phenomena may be expressed. This ter- 

 minology and these concepts are particu- 

 larly useful, because they are derived from 

 the idea of mechanical work, which is one 

 of the most immediate and familiar of the 

 concepts drawn from daily experiences. 

 Most commercial accounts are ultimately 

 balanced in terms of work or energy. 



In using the idea of energy as a solvent 

 for unifying and organizing instruction in 

 physics it is not in the least necessary to 

 become an " Energetiker, " to deny the ex- 

 istence of everything but energy, and to 

 rule out the imagination and speculation 

 concerning atoms and the like. The idea 

 is one easily grasped by any one, since it is 

 drawn from such universal experience. It 

 can be visualized in the lifting of heavy 

 objects so as to be made very concrete. In 

 my opinion this idea offers a fruitful field 

 for experimentation in the teaching of the 

 elements of physics. 



Another fruitful suggestion has been 

 made by Dr. Northrup in the Journal of 

 the Franklin Institute for March, 1908. 

 It is to use analogy — not poetic analogy, 

 but strict analogy, such as exists between 

 translatory and rotary motion. This same 

 suggestion was made by Professor Henry 

 Crew at the meeting of the Central Asso- 

 ciation of Science and Mathematics Teach- 



