76 



Barrktt, Brown & Hadfield — On the Electrical Conductivity and 



added, or 6'6 microhms for 1 per cent, of carbon. The rate of increase of 

 resistance for a given increment of carbon being some four times greater in tlie 

 former case than in the latter. This rapid fall of conductivity for the first small 

 additions of carbon is seen in fig. 2 and Plate II. 



Alloys of Iron and Manganese. 

 We will next take the alloys of Iron and Ilanganese, of which an extensive 

 series was made for this investigation. This series may also be subdivided 

 into two groups, Series A and B, the latter containing higher carbon. 



Group 2. — Alloys of Iron and Manganese (Series A). 



Alloys of Ikon and Manganese (Series B). 



* 1379 B also contains 0-13 per cent, of silicon, 

 f 1379 D also contains 0-63 per cent, of sUicon. 



