Messrs. H. Nagaoka and K. Honda on Magnetostriction. 269 



Nickel shows always diminution of volume, and the change 

 is greater than in iron. 



From figs. I, 5, 6 w r e gather the following facts : in low 

 field the change is very small, it then goes on increasing 

 rapidly until it reaches the " Wendepunkt," whence to increase 

 steadily though at a slower rate. 



For feeble magnetization the change of volume is very 

 small ; but with the strong, the change is nearly proportional 

 to the square of the intensity of magnetization. Compared 

 with Dr. Knott's measurements, we find that the initial 

 behaviour of nickel as regards the internal and external 

 volume-changes is different, Dr. Knott finding the increase 

 of internal volume. In other respects the quality of the 

 change is similar, but the amount is nearly ten times smaller 

 in the present experiment than the determination of Dr. Knott 

 on the internal volume of the nickel tube ; Cantone's deter- 

 mination with nickel ovoid is twice as large as in the present 

 measurement. 



Change of Length by Magnetization. — It would be superfluous 

 to give minute details of the measurement of the change of 

 length by magnetization. The apparatus was the same as 

 that used by one of us * some years ago in the measurement 

 of hysteresis accompanying the change of length. It con- 

 sisted of a single optical lever with arrangement for tempe- 

 rature compensation on the same principle as the gridiron- 

 pendulum. The mirror described in the former paper was, 

 on this occasion, replaced by a small right-angled prism. 



The measurements of the lenoth-cbange in iron and nickel 

 are given in the following table, with the corresponding values 

 of H and I. 



Iron Ovoid. 



Nickel Rod. 



H. 



I. 



T xl ° 7 - 



3 



250 



l-i 



6 



780 



11-3 



8 



920 



22-7 



14 



1160 



23-3 



30 



1270 



331 



51 



1340 



31-6 



86 



1420 



28-0 



113 



1460 



23-8 



151 



1500 



16-6 



210 



1560 



8-3 



253 



1600 



2-5 



306 



1650 



-6-4 



1 



H. 



I. 



r xl ° 7 - 



15 



143 



-11-3 



53 



315 



-694 



74 



355 



-95-3 



98 



394 



-124-0 



122 



414 



-1426 



177 



444 



-172-8 



255 



474 



-190-8 



337 



483 



-207-0 



507 



485 



-216-5 



* Nagaoka, Phil. Mag. Jan. 1894 ; Wied. Ann. vol. liii. p. 487 (1894). 



