460 Intelligence and Miscellaneous Articles. 



where n is the refractive index of gases for infinitely long waves. 

 In this way we get for 



Hydrogen at 4°-4.. 6 =:0-0 3 5244 (Waals); w=O0 4 938 ; A=5-69, 

 Ethylene at 101°.. b = 0-0 2 254 (Waals); w=O0 3 467; A=5'62. 



From this we have as the mean 



A = 5-655 = 4 s/2. 



Exner's Rep. vol. xxvii. p. 369, 1891 ; from Beiblatter der Physik, 

 No. 8, 1892, p. 503. 



ON THE THEORY OF THE USE OF A PERMANENTLY MAGNETIZED 

 CORE IN THE TELEPHONE. 



In No. 208 of this Journal Dr. Trouton has explained the 

 meaning of the permanent magnet in telephonic receivers. 

 Although his explanation is undoubtedly true, there is a second 

 side to the question that he has wholly left alone. 



According to my investigations, the permanent magnet in the 

 telephone plays two roles, quite different from each other : — 



1. It serves to give the sounds the required loudness. 



2. It serves to give the sounds the true pitch. 



My researches have shown me that when a non-polarized 

 telephone is joined to the secondary of an induction-coil, in the 

 primary of which a microphone is placed, the sounds given out by 

 the telephone are an octave higher than those produced before 

 the microphone. Of course it follows from this, that such a 

 telephone will be unable to speak intelligibly, as all the vowels 

 lose their character by this change of pitch *. 



The experimental proof of this fact is very difficult, owing to 

 the inevitable remanent magnetism of every iron core and also to 

 the feebleness of the sounds given by a non-polarized telephone ; 

 but is very easily proved when a speaking condenser is used 

 instead of a telephone. 



For my experiments on this subject, I refer to my papers 

 " La Polarisation des Eecepteurs Telephoniques " and " l'Emploi 

 de la Pile auxiliaire dans la Telephonie," which are to be found 

 in the Archives Neerlandaises, t. xix. and t. xx., 1884 and 1885. 



J. W. GlLTAY. 



Delft, October 2, 1892. 



* The vowel thus becomes A, pronounced as in Dutch or in French, 

 hut the other vowels are quite lost. 



