82 Barrktt, Bkotvn & Hadfield — On the Electrical Conductivity and 



The unannealed results are i^lotted 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 3^ and 15i per cent, of tungsten 



Eer-cema.ffs- of Tu.ihjsteTV 



Fig. 5. 



in the alloy, the increase of specific resistance is 8'6 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. 



