568 



Messrs. K. Honda and S. Shimizu on 





JSickel-Steel 24*04 per cent. 





*=21°-0C. 



^=-186 c O. 



*=23°-QC. 





U 





SI 





ol 



H. 



1 x 106 - 



H. 



T XlOe. 



H. 



7 x 106 - 



22-9 







34-3 



07 



35-3 



10 



76-5 



01 



657 



2-5 



66-7 



2-9 



196-6 



0-2 



1240 



59 



112-0 



5-4 



2817 



03 



238-5 



99 



253 



10-0 



429 



035 



334 



13-3 



398 



12-7 



600 



0-6 



468 



17-8 



508 



144 



808 



07 



622 



21-6 



695 



15-9 







835 



25-6 



858 



169 



The effect of cooling on the magnetic elongation in nickel- 

 steels is exactly parallel to the same effect on magnetization. 

 In nickel-steels containing percentages of nickel greater than 

 28" 74 per cent., the elongation is diminished in weak fields 

 and increased in the .strong, by cooling them in liquid air ; 

 with other nickel-steels, the initial decrease of elongation 

 vanishes. 



The ratio of the elongation in liquid air to that at ordinary 

 temperature increases in strong fields, as the percentages 

 of nickel decrease. In 36 per' cent. Ni, it amounts to about 

 1*6 in H = 500 c.g.s. ; and in 28*32 per cent. Ni to 3*7, and 

 in 24*40 per cent. Ni to 160 for the same field. 



For reversible nickel-steels, the elongations after and before 

 cooling coincide with each other. The elongation of other 

 nickel-steels, once cooled in liquid air, is always greater than 

 that before cooling. With 26*64 per cent, and 2440 per 

 cent, alloys, the elongation is even increased, by heating it to 

 the ordinary temperature. 



25 per cent, nickel -steel does not sensibly elongate at 

 ordinary temperature nor in liquid air. 



fg) Change of Density by Cooling. 



The densitjr of the irreversible nickel-steels at ordinary 

 temperature suffered a permanent change, if they were once 

 dipped in liquid air. This singular fact was first observed 

 by Hopkinson *. The following table contains the observed 

 values of density : — 



* Hopkinson's Original Papers, vol. ii. p. 240. 



