114 Barrett, Brown & Hadfield — On the Electrical Conductivittj and 



U^D to nearly 4 per cent, of nickel the hysteresis loss increases but slightly, 

 being less than that occurring with a corresponding addition to iron of any other 

 element, so far tried, except aluminium and silicon. As before stated, an increase in 

 magnetic hardness occurs at about 4 per cent, of nickel, and hence the hysteresis 

 loss is seen to rise suddenly in the specimen 1267 B. The reverse effect produced 

 by still larger additions of nickel is also well seen, the change taking place at 

 about 20 per cent, of nickel. The increase of permeability in the last specimen 

 is remarkable, a rod of this alloy being practically saturated in a field of about 

 16 C.G.S. units. Notice also the opposite effects produced by annealing in the 

 different percentages of nickel. 



The great permeability of the low and very high nickel steels is remai'kable, 

 and ought to be determined for still lower magnetising forces. It was noticed 

 that under the feeble force of the Earth's magnetic field the high nickel steel, 

 1449 (annealed), had a higher permeability than a specimen of the very best 

 iron. In a future series of experiments the magnetic properties of these and 

 the silicon and aluminium steels under small magnetic forces, and at different 

 temperatures, will be investigated. 



The effect of annealing on the magnetic properties of alloys is further 

 seen in a striking manner in Plate V., which contains the B and H curves of a 

 nickel chromium, and a manganese chromium steel, compared with good iron and 

 a low manganese steel. 



Table VIII. — Effect of Annealing (Plate V.). 



It will be seen that whilst the annealed specimens of 1430 A and 1450 A are 

 magnetic, the former strongly so, the uuannealed specimens are only slightly 

 magnetic in a field of 45 C.Gr.S. units. In the steel 1420, with 0'5 per cent, of 

 carbon, the coercive force is doubled in the unannealed specimen, that is to say, 

 the hardness in the two states differs widely. 



* This specimen also contains 1-3 per cent, of carbon. 



t These values were too small to bo estimated, the specimens being almost non-magnetic, in the field. 



