122 PROCEEDINGS OF THE AMERICAN ACADEMY 



mission of electrical waves through a dielectric, the following experi- 

 ment was tried. A glass Leyden jar, 2.5 cm. in diameter and 28 cm. 

 in height, connected with our inductance circuit, was placed inside a 

 coil consisting of 728 windings of large wire. The outer and inner 

 radii of this coil were 27.7 cm. and 34 cm. Its height was 40.5 cm. 

 The magnetic field iu this coil was supplied by a Gramme machine, 

 which gave a current through the coil of approximately thirty amperes. 

 It was expected that a certain amount of the energy spent in pro- 

 ducing the electrical waves would be consumed in a reaction on the 

 magnetic field. The total duration of the electrical discharge did not 

 appear to be notably affected by the magnetic field. Certain experi- 

 ments seemed to show a decrease in the total number of electrical oscil- 

 lations. A large number of experiments will be necessary to decide 

 upon the effect of a magnetic field upon the passage of electrical waves 

 through a dielectric. The difficulty of obtaining an electrical dis- 

 charge under the same difference of potential made the experiment an 

 extremely difficult one. The method seems to us to promise a dis- 

 covery of Maxwell's displacement currents in dielectrics ; and we are 

 therefore continuing our researches in this direction with a modified 

 form of apparatus. 



Conclusions. 



1 . The electrical oscillations in the air between the plate of an air 

 condenser show a periodicity extending through the entire range of 

 oscillations. We believe that this periodicity is the analogue of the 

 phenomenon of Hysteresis in Magnetism. A certain amount of the 

 energy of the electrical discharge is spent in overcoming the dielectric 

 viscosity of the air, and in straining the air dielectric. This sti-ain is 

 not immediately released in unison with the electrical surgings. 



2. The discussion of our entire results shows unmistakably that 

 electrical oscillations in air are not represented fully by the theoretical 

 equations employed by Hertz. Since the latter writer has taken the 

 term resonance from the subject of acoustics, and has given it a new 

 significance in relation to electrical waves, we are tempted to draw 

 also an analogy from the subject of sound. Laplace showed that 

 the discrepancy between the value for the velocity of sound in air 

 calculated from the theoretical equation, and that obtained by experi- 

 ment, was due to a transformation of energy in heating and cooling 

 the air during the passage of the sound wave. Our experiments ou 

 the transmission of electrical waves through the air shew also that the 

 values calculated from the theoretical equation do not agree with the 



