534 SCIENCE PROGRESS 



positive potential, the other is found to rise to the same poten- 

 tial by induction, the charges on either plate being very small ; 

 if the second be now earthed, a large positive charge flows to the 

 first plate and an equal negative charge is induced on the second, 

 as was seen previously. If both are then insulated and the first 

 earthed, the potential of the second will fall to the same numerical 

 value as before but negative. ,So it is seen that the potential of 

 a body depends on that of its neighbours as well as on its charge. 

 The principle is then applied to produce a charge at high 

 potential; an insulated plate is connected to the live main, a 

 sheet of paraffined paper is laid on it and on that a second plate 

 with an insulating handle. The second plate is earthed and 

 then removed and the potential rises so much that a spark can 

 be taken from it. The substitution for the first plate of a rubbed 

 sheet of ebonite, forming the ordinary electrophorus, demon- 

 strates the production of electricity on ebonite by friction ; 

 the Wimshurst machine can then be introduced, if it be con- 

 sidered desirable to use it to show some of the properties of 

 electricity at high potential. 



To return to broader views, the basis of these proposals is 

 the belief that school conditions make it highly expedient to 

 modify the development of the subject so that it may be suitable 

 for ordinary boys of fourteen or fifteen and at the same time 

 may form a satisfactory introductory course for boys who will 

 pursue the study of science up to a much more mature age. 

 This object can probably be effected in more ways than one but 

 the modifications which are proposed have been shaped in the 

 belief that young boys learn more science if they are set to use 

 actual tools and instruments in solving real problems, best of all 

 if they use them on real tasks. The exigencies of teaching large 

 classes often make this ideal impracticable but we can aim 

 either at approximating to it as closely as circumstances permit 

 or at hurrying the boy as rapidly as possible away from what he 

 feels is the real thing and translating him into the realms of 

 abstraction. To be profitable, abstraction requires a consider- 

 able concrete foundation. Therefore, so far as possible, every- 

 day commercial instruments and conditions have been chosen in 

 place of the usual apparatus to be found in lecture rooms and 

 instructional laboratories, which appears to be designed primarily 

 to materialise the ideal diagrams of the text-book and secondarily 

 for verifying the results and laws therein reached by deductive 



