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XXXI. On the Electrical Conductivity of Copper fused with 

 Mica. By Sub-Lieut. A. L. Williams, R.JST., with Intro- 

 duction by Prof. J. C. McLennan, F.R.S.* 



[Plates Y.-YIL] 



Introduction. 



"TTTHILE acting as Scientific Adviser to the Admiralty, I 

 ▼ T had my attention drawn by Sub-Lieut. A. L. Williams, 

 R.N., to some experiments made by him in the early part of 

 1919 at Cambridge, in which he found that samples of copper 

 when fused with mica exhibited a remarkably large fall in 

 resistance when gradually subjected to rising temperatures. 



During a short furlough he was given an opportunity at 

 the Admiralty Physical Laboratory, South Kensington, to 

 develop this discovery and, on going back to duty, he left 

 with me some notes embodying the results of his work. 

 I have not had an opportunity of communicating with him 

 again, but as the results are interesting it is thought they 

 should be duly recorded. His experiments are described 

 below, and accompanying them are some additional notes of 

 results obtained at the University of Toronto by Miss Isabel 

 Mackey and Miss I. Giles, who have followed up the subject 

 still further. J. 0. McL. 



A. 



Experiments by Sub-Lieut. A. L. Williams, R.N. 



I. Preparation, 



The samples for test were all prepared in the open on a 

 piece of iron or copper plate — used as an anode — and a 

 carbon rod as the cathode, the arc being struck at first 

 between the plate and carbon, and then, when hot, to the 

 mixture. The mica was first melted . then the copper added. 

 In making up the samples studied, about equal proportions 

 of copper and mica were used. 



II. Effect of Temperature. 



Resistance temperature measurements for two samples 

 were made for a range of temperatures from 27° to 850° C. 

 For sample A, the curves of which are attached, Graphs 1 

 and 2 (PI. V.), the resistance fell from 1G,000 ohms at 27° C, 

 to 0-5 ohm at 850° C. 



* Communicated by Prof. J. C. McLennan. 

 Phil. Mag. Ser. 6. Vol. 40. No. 237. Sept. 1920. U - 



