TEMPERATURE ON THE MAGNETIZATION OF STEELS, ETC. 13 



In the first place, the increase in the magnetization at 500° 

 is nearly double the intensity at ordinary temperatures. The 

 maximum intensity at about 500° is highly characteristic of this 

 metal, for the decrease in the intensity takes place quite steeply 

 as the temperature is further increased. The place of sudden 

 decrease is carried to higher temperatures as the magnetizing 

 forces become stronger. The cooling curve cuts the heating 

 curve and reaches the maximum at about 300°, which is about 

 140° lower than that for heating. The change of magnetization 

 either on cooling or on heating wears a rather irregular aspect, 

 of which it is not easy to give a simple description, but the 

 inspection of the curves will reveal the complicated nature of the 

 change. 



§ "). Recalescence of Tungsten steel. The curious behaviour 

 of tungsten steel on cooling after heating seemed at first sight to 

 have an intimate connection with recalescense ; it can be easily 

 observed in the case of a rod of this metal. Upon heating it 

 with the burner described above to about 800°, and then expos- 

 ing it to the air, and observing the dazzling metal in the dark, 

 we first notice a shade of dusky hue at both extremities ; this 

 gradually spreads upwards and downwards, just as dilute ink 

 soaks into a red blotting paper. The dark portions gradually 

 spread toward the middle of the rod, but with the lapse of time, 

 the ends begin again to brighten. The colour now somewhat 

 resembles that of the setting sun just emerging from a thick 

 cloud ; that part of the rod, which a few minutes before was 

 scarcely visible, becomes tinged with red, and the clouds recede 

 towards the middle, where they meet and disappear. The somber 

 red thus prevails throughout the reheated rod, till it fades to a 

 faint glimmer and disappears in complete darkness. 



