﻿488 Mr. M. H. Belz on the Heterodyne Beat Method 



The wave-length was 725 metres. The results are included 

 in Table II. 



Table II. 



Specimen. 



Copper 

 Brass 



Constantan 



Capacity Change 

 (arbitrary units). 



201 

 190 



98 



Frequency Change 

 per second. 

 dn. 



1027 



961 



501 



The wires of platinoid, manganin, and constantan used in 

 the above tests contained 15 per cent., 4 per cent., and 

 40 per cent, nickel respectively. The magnetic suscepti- 

 bilities o£ copper-nickel alloys have been determined by 

 Gans and Forseca *, who found that when the nickel 

 content was 40*4 per cent, the susceptibility was onlv 

 0*189 xlO -6 cg.s., being much smaller for lower perr 

 centages. The effect of the susceptibilities of the specimens 

 used on the frequency changes can thus be neglected. 



Fig. 2. 



t 



k 



*< 800 



8? 600 



b 400 



5 



* 200 





















- & 





■^A 











y^ 











1 















• / 















J 











_ 





6x|0- 



*■ Specific Cont/uCtir/ty, K, rfi.h.o.s. 



The specific conductivities, K, in mhos cm -1 ., of the 

 materials used, taken, with the exception of brass, from 

 Kaye and Laby's tables, are :— for copper, K= 6*29 X 10 5 , 

 for platinoid, K = 0*291 x 10 5 ,for manganin, K = 0*233 x 10 5 , 

 and for constantan, K = 0*204 x 10 5 . The specific conduc- 

 tivity for the brass used was determined to be K = 1*182 x 10 5 . 



Fig. 2 represents the relations obtained by plotting dn 

 against K, curve (a) referring to test (a), curve (b) to test (b). 



* Gans u. Forseca, Ann. d. Phys. vol. lxi. p. 742 (1920). 



