ELECTRICAL OSCILLATIONS. 



479 



provided with a screw, by which it can be moved parallel in each 

 case until the condition is realised. 



A dielectric plate D of thickness e is introduced between A and 

 A I} and, by means of a micrometric screw M, the displacement d 

 of the plate A x is measured which is necessary to re-establish equi- 

 librium ; this gives the specific inductive capacity. 



As this inductive capacity is a function of the time of charge, 

 the conductors C and A l B l are connected with the poles of an 

 induction coil, the inducing current of which is broken by a 

 vibrating plate, or by a rotating electromagnetic apparatus, which 

 can give as many as 12,000 breaks in a second. 



Mr. Gordon investigated a great number of substances. He 

 found that for glass, in particular, the manner in which the surfaces 



Fig. 227. 



are cleaned plays an important part, and that the spontaneous 

 alteration which they undergo in the course of time manifests itself 

 by a material increase of apparent inductive power. 



1069. ELECTRICAL OSCILLATIONS. The theory of electrical 

 oscillations (538) furnished Schiller* with a method which has 

 the advantage that the results correspond to a smaller time of charge 

 than any other. 



The general nature of the experiment has been mentioned above 

 (911). The time T of a single oscillation is given by the formula 



T 2 = 



i R 2 ' 



/-i T TO 



CJL AL^ 



* SCHILLER. Pogg. Ann., Vol. CLII., p. 535. 1874. 



