﻿578 Intelligence and Miscellaneous Articles. 



the time of adjustment or distribution of energy among the degrees 

 of freedom should not extend to long periods. 



The difficulties connected with any considerable increase in the 

 duration of the experiments will undoubtedly be great, as it will 

 be necessary to maintain the temperature so very uniform ; but 

 we hope shortly to attack the problem again from this point of 

 view. 



I am, Gentlemen, 



University College, Bristol, Yours obediently, 



November 12, 1894. A p Qhattock. 



ON THE PROPAGATION OF ELECTROMAGNETIC WAVES IN ICE, 

 AND ON THE DIELECTRIC POWER OF THIS SUBSTANCE. BY 

 M. BLONDLOT. 



In a previous note (Comptes Meadas,Ju\j25, 1892) 1 enunciated 

 the following proposition: — The length of the waves which an 

 electromagnetic oscillation can emit is the same whatever be the 

 insulating medium in which the experiment is made; in other 

 words, the wave-length depends on the oscillator alone, just as in 

 acoustics the wave-length of a pipe depends only on the length of 

 the pipe. 



The confirmatory experiments described in the Note cited 

 referred to oil of turpentine and to castor-oil; the law holds 

 perfectly for both these substances, and everything leads to the 

 belief that this will be the same for other dielectrics. 



There is, however, a doubt about ice, in consequence of the 

 exceptional properties ascribed to it. The experiments of M. Bouty 

 (Comjptes Rendus, March 7, 1892) show in fact that ice has a di- 

 electric power of 27, that is to say incomparably greater than that 

 of all other substances. Suspecting that the law relative to the 

 propagation of waves might not apply to a dielectric so different 

 from the others, I resolved to submit the question to experiment. 



For these investigations I availed myself of the intense and 

 prolonged frosts of the winter of 1892-93. M. M. Dufour has 

 helped me in carrying them out, which the rigour of the cold 

 rendered difficult and even painful. I thank him for his extreme 

 kindness on this occasion. 



The method which I adopted was the following, which, with 

 slight modifications necessitated by the solid character of the di- 

 electric, is the same as that I used in the case of turpentine and 

 castor oil. 



Electromagnetic waves were transmitted along two tinned copper 

 wires 2-5 millhn. in diameter, stretched horizontally and parallel 

 to each other at a distance of 0*8 metre. A resonator of gilt 

 copper is placed in a fixed position between the wires ; the portion 

 of the transmitting wires beyond the resonator is contained in a 

 wooden trough 4 metres in length. The trough being filled with 

 liquid, the position is sought at which a movable bridge must be 

 placed joining the wires beyond the resonator to cause the spark 

 to disappear ; the distance from the bridge to the resonator is then 



