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XVI.—Efects of Strain on Electric Conductivity. By August Wi1TKoWSKI. 
(Communicated by Str WILLIAM THomson.) 
(Read 21st February, 1881.) 
In the following communication an account is given of some experiments 
made in the Physical Laboratory of the Glasgow University, whose object was 
the measurement of the change of conductivity produced by strain in a metal 
conductor. 
Two constants are required in order to determine this alteration in the most 
general case of a homogeneous isotropic conductor, strained in any way, as may 
be easily inferred from the analogy with elastic strains and stresses, constants 
expressing the change produced by uniform cubical compression and by simple 
distortion. The determination of the latter for brass is the object of the pre- 
sent paper. 
The method proposed by Sir Witt1aAm Tuomson for this purpose is shortly 
described in the Proceedings of the Roy. Soc. 1879. Str W1tL1Am THomMsoN has 
added arrangements admitting of accurate measurements, consisting of ap- 
paratus represented in the annexed diagram, which may be described as 
follows :— 
Fia. 1. 
R is a brass tube (length=17°8, external diam. =1°48, internal diam. = 1-29 
cm.) fastened firmly by means of a collar and screws to the wooden support P, 
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