﻿and some Applications to Physical Measurements. 487 



conductivity of the specimen. This solution had a con- 

 ductivity far greater than any of the magnetic specimens, 

 which were examined in liquid, crystal, and powder forms, 

 but, counting over periods ranging beyond ten seconds, no 

 variation in the beat note was observed. Accordingly it 

 was assumed that the effect in the magnetic substances was 

 negligible. 



Some tests were then made with different lengths and 

 sizes of graphite taken from ordinary pencils. The con- 

 ductivities of these specimens were much greater than that 

 of the solution of acid, but there were no changes in the beat 

 note indicating an increase of frequency. In the case of 

 some specimens changes occurred which corresponded to an 

 increase of inductance, but some iron must have been present 

 in them. 



Finally, some tests were made on different specimens of 

 copper, brass, manganin, platinoid, and constantan wires. 

 In these experiments, which were carried out after the 

 susceptibility determinations, some alterations in the elements 

 of the circuits enabled the heterodyne note to be obtained 

 by beats produced between the fundamental oscillations. 



It is interesting, at this stage, to give the results obtained 

 for the variation in frequency change with the conductivities 

 of the specimens. In this connexion two tests were made, 

 the first employing small specimens and counting the beats, 

 the second emploving large specimens and computing the 

 frequency change From the alteration in capacity necessary 

 to bring the heterodyne note to coincidence with the auxiliary 

 note. 



(a) The specimens used were wires of copper, brass, 

 platinoid, and manganin, each of length 0*32 cm., and 

 diameter 0'711 mm. The wave-length was 710 metres. 

 The results are included in Table I. 



Table I. 



Frequenc)' Change 

 Specimen. per second. 



dn. 

 Copper 9*54 



Brass 4'88 



Platinoid 0-33 



ranin 0-28 



(b) The specimens used were wires of copper, brass, and 

 constantan, each of length 8 cm. and diameter 2*03 mm. 



