82 ~ Barrett, Brown & HaprreLp—On the Electrical Conductivity and 
The unannealed results are plotted in the next curve; the more rapid fall in 
the first part of the curve is partly due to the greater purity of the first specimen 
1294 F. Annealing, it will be noticed, produces a great increase in the con- 
ductivity of the higher tungsten steels. The effect of tungsten on the conduc- 
tivity of pure iron is less than that of any other added metal which we have so far 
examined (except in the case of copper, the results of which are indefinite, see 
p. 85): this will be seen from Plate II. Between 33 and 15} per cent. of tungsten 
Conductwety Pure Copper = 
Ber-centage of Langsten 
Fre. 5. 
in the alloy, the increase of specific resistance is 86 microhms, which is equivalent 
to an increase of 0°72 microhms for every one per cent. of tungsten added to the 
iron. Comparing 1294 H and I, the increase of specific resistance for one per 
cent. of added tungsten is only 0:3 microhms, these specimens being more 
comparable as they contain nearly the same amount of impurities; for lower 
percentages the rate of increase is higher. 
Aluminium Steels. Silicon Steels. Chromium Steels. 
The next group, alloys of aluminium and iron, are remarkable for their 
extremely low order of conductivity. 
