MAGNETIZATION AND MAGNETIC CHANGE OF LENGTH. 



51 



Comparing the above values for ordinary temperature with 

 het corresponding values in the first experiment, we notice that 

 except with Sß^o nickel steel, the magnetizability of these alloys 

 had slightly changed by the repeated heating and cooling, which 

 the alloys underwent, since the end of the first experiment. 



From these results, the curves of magnetization to tempera- 

 ture are obtained and given in Fig. 7 a, b, c, d. In these figures, 

 we have also included the results obtained in our first and second 

 experiments. As seen from the figures, the diminution of mag- 

 netization, after the critical point is reached, is very slight ; and 

 to judge from the course of the curve, it seems probable that the 

 magnetization does not altogether vanish, till the melting points 

 are reached. 



The curves of magnetization at a constant field in the ascend- 

 ing and descending stages of temperature do not exactly coincide 

 with each other when the range of temperature is large, the two 

 curves thus enclosing a small area between them. 



As the critical points of these nickel steels for H =400, we 

 give the following values : — 



These values nearly coincide with those of M. Osmond and L. 

 Dumas. Thus the critical point decreases with the percentage 

 content of nickel. 



The manner, in which the magnetization of irreversible nickel 

 steels changes with temperature, is very striking. The observed 

 values are given in Table XII. 



