440 Hormell — Dielectric Constant of Paraffins. 



Table III shows the final results. The last two sets of read- 

 ings shows the comparison of waves produced w T hen the Lecher 

 wires were kept constant and the secondary of the Blondlot 

 oscillator changed. In the first case the secondary was made 

 of copper wire and in the second it was of iron. Great care 

 was taken to make the two secondaries of the same size and 

 shape and to keep the primary and secondary the same dis- 

 tance apart in both cases. 



Allowing less than one per cent for error of observations, it 

 is readily seen that the wave lengths for different kinds of wires 

 are practically the same. One concludes from these observa- 

 tions that conductors offer no resistance to the passage of short 

 electrical waves, and that the magnetization of iron is not able 

 to follow 7 oscillations as high as 800,000,000 per second. These 

 conclusions agree with those of Hertz* and Lodge.f But St. 

 John J found a difference of wave length in iron and copper of 

 from \\ to 3 per cent. , This difference, however, was for 

 oscillations of 115,000,000 reversals per second. 



Dielectric Constant of Paraffin. 



Maxwell has shown theoretically that the dielectric constant 

 of a substance is equal to the square of the index of refraction. 

 The index of refraction of a given substance for electrical 

 waves as well as for light waves is the ratio of their relative 

 velocities in air and in the given substance. But since the 

 ratio of the velocity is equal to the ratio of the wave lengths 

 we have 



K=u 2 = (p- Y where 



="• = (£> 



A a = the wave length of a given electrical disturbance in air. 

 X s ■— the wave length of the same electrical disturbance in the 



given substance. 

 p = index of refraction. 

 K = dielectric constant. 



The Blondlot oscillator offers a unique and very satisfactory 

 means of measuring the wave length in air and in the given 

 substance. This means is satisfactory because one is able to 

 keep the oscillator in a constant condition, thus making the 

 wave length in air a constant for a given combination. The 

 method of securing the wave length in air has been described, 

 and it now remains to indicate the way in wmich the wave 

 length in paraffin may be obtained. 



* Electric Waves, p. 113. 



•}• Modern Views of Electricity, p. 101, 1889. 



X Proceedings of American Academy, p. 218, 1894. 



