91 
1906-7.] Heusler’s Magnetic Alloy. 
saturation value of I, with a slight augmentation of the hysteresis (fig. 2, 
curve 4). The specimen was laid aside for nearly ten months, and in this 
interval almost recovered its original susceptibility, while the dimunition 
in the hysteresis which had been effected by the quenching was only 
reversed to a very slight extent. 
The quenching tests were again resumed and cycles obtained for the 
following series of temperatures : 400°, 450°, 500°, 555°, 610°, 660°, 712°, and 
745°. At each stage three tests were made : (1) with the quenched specimen, 
(2) with the specimen immersed in liquid air, and (3) with the specimen 
back to atmospheric temperature. Fig. 3 exhibits the nature of the results 
Effect of Quenching on Permeability 
Fig. 3. 
obtained in this investigation. The abscissae represent the temperatures of 
quenching, and the ordinates give the permeability corresponding to a field 
of 20 C.G.S. units for the specimen in the quenched condition. The lower 
curve shows the values obtained in the cycles at ordinary temperature ; 
those obtained with the specimen in liquid air are shown in the upper 
curve. It will be noticed that there is a very marked diminution in 
permeability on quenching at 610°, and on quenching at higher tempera- 
tures the quality is to a considerable degree restored. 
Throughout the investigation there were traces of cracking in the 
specimen due to the quenching, and this would probably affect the magnetic 
tests to a slight extent. While being heated in the furnace preparatory to 
quenching at 800°, the specimen broke in two. An examination of the 
sections of fracture showed that a decided change in constitution had taken 
