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Mr. S. R. Roget. Effects of prolonged 



It appears that there is a temperature in the neighbourhood of 

 180 C., for which the maximum increase of hysteresis is greatest. 

 With higher temperatures the hysteresis, although rising more rapidly 

 at first, docs not reach so high a maximum value and begins to fall 

 sooner and faster, tending apparently to a lower steady state the 

 higher the temperature. An example of this is shown in curve 7, 

 fig. 1 (temperature 260 C.), where a fairly low and nearly steady 

 state is reached in the last days of the heating. In this instance it 

 took the iron only about a quarter of an hour to reach its maximum 

 of hysteresis, which was only 91 per cent, higher than the initial 

 value. 



Fig. 2 shows the earlier stages of the action for temperatures 

 of 125 C. and over. It will be noticed that the peak at which the 

 hysteresis reaches its maximum in each case comes sooner the higher 

 the temperature, and that its height becomes reduced when the 

 temperature is high. The absolute values of the hysteresis in the 

 experiments to which these curves relate are given in Table II. 



It is probable that the attainment of a maximum value followed 

 by a decrease is not confined to temperatures above 135 C., and it 



