Conductivity of Copper fused with Mica. 283 



G. Attempts were made to make up similar compounds 

 with the following metals and mica: — 



Tin. The metal vaporized at too low a temperature. 

 Silver. Did not combine. 

 Platinum. Did not combine. 



Iron. Combined, but no resistance temperature measure- 

 ments were made. 



B. 



Experiments by Miss Mackey. 



I. Experimental Arrangements. 



(a) The samples to be tested were all made in the open on 

 a piece of iron plate used as an anode and a carbon rod as a 

 cathode. The current was controlled by a large rheostat 

 giving up to 30 amperes on the 110 D.c. circuit. An arc 

 was struck between the plate and carbon and, when hot, the 

 mica was melted and the other material added. 



(b) A quartz tube closed at one end and covered with 

 nichrome wire was used as a receptacle in which to melt the 

 material and form it into a regular cylindrical shape for 

 experimental work. 



(c) A small electrical furnace was used to heat the 

 material. It consisted of a circular porcelain foundation 

 covered with wire and all was covered with asbestos except 

 the two binding posts. 



II. Results. 



(a) Mica and Copper. — Mica and copper were fused on 

 the iron plate into small lumps, and some of these were then 

 finely ground into powder. No traces of 'mica or copper 

 could be detected, only a uniform dull black powder. The 

 powder was put into a quartz tube and heated, but this did 

 not prove a satisfactory method of obtaining the mixture in 

 the form of solid rods, as. part of the mixture fused with the 

 quartz, and it was found impossible to separate the two 

 substances. When the quartz was broken, the copper-mica 

 was found to be very brittle and not at all suitable for 

 resistance measurements. Plntinum wires were then fused 

 into the ends of the copper- mica lumps which had not been 

 powdered, and the variations in the resistances of these 

 Jumps were observed when they were raised to various 

 temperatures. 



U2 



