1912-13.] Application of the Law of Torsional Oscillation. 193 
Observations on a Compound Wire. 
It was formerly seen* that a specimen of copper wire when stretched to 
the limiting tension of rupture gave one line only, with the values 
a— 18, n — 1 ‘05, 
and also that zincf had a similar curve with a straight line got when 
a = 0, n=*60, 
and the effect of electrolytically depositing a gradually increasing coating 
of zinc on a specimen of stretched copper was observed. Twelve experi- 
ments in all were carried out, a deposit of - 8 gram of zinc being added in 
stages by the decomposition of a solution of ZnS0 4 . The wire was 
thoroughly cleaned and momentarily dipped in acid before being immersed 
in the solution, and it was found that a fairly uniform coating could be got 
until ’8 gram of zinc had been added to the copper wire (of initial 
weight ’69 gm.). After this point the depositions became irregular and 
non-adherent. It was found on plotting that the straight line originally 
got for copper gradually and uniformly altered, giving a lesser and lesser 
value of n, until the value approached that of zinc itself. Accurate values 
of n could not be got, however, since a wavy curve was got in each case, 
due to pendulum swings set up in the oscillator on account of the slight 
irregularities of deposition. By taking a copper core of very small 
diameter an attempt was made to obtain practically a deposited zinc wire ; 
but, although such a wire was obtained, the lightest oscillating ring obtain- 
able with suitable moment of inertia was of sufficient weight to snap 
the wire. 
* Proc. Roy. Soc. Edin vol. xxv. p. 437. 
t Ibid., p. 438. 
{Issued separately May 19, 1913.) 
VOL. XXXIII. 
13 
