334 Proceedings of Royal Society of Edinburgh. [sess. 
Further Note on the Volume Changes which accompany 
Magnetisation in Iron and Nickel Tubes. By Pro- 
fessor C. G. Knott, D.Sc., F.R.S.E., and A. Shand, Esq. 
(Read February 18, 1895.) 
In our last communication (read July 2, 1894) we gave the broad 
results for three nickel tubes of various bores (see vol. xx. p. 296). 
In these experiments the screw stopper through which the capillary 
glass tube passed was made of brass. This brass stopper was used 
because of the comparative difficulty of working nickel. We were 
led, in the course of some tentative experiments, to use this brass 
stopper with one of the steel tubes. Now, in the earlier experi- 
ments with the iron and steel tubes, we had used an iron stopper. 
We were hardly prepared, however, to find that the mere substitu- 
tion of a brass for an iron stopper should produce such a marked 
effect, not only on the amount of change of volume in given mag- 
netic fields, but also on the manner in which the volume change 
varied as the field increased or decreased steadily. 
This result at once proved that it was absolutely necessary to 
furnish the nickel tubes with a nickel stopper ; and, in the present 
note, we give a comparison of the volume changes in Steel Tube Y. 
with (1) an iron stopper, (2) a brass stopper, and of the volume 
changes in Nickel Tube I. with (1) a nickel stopper, (2) a brass 
stopper. The numbers in the first column give the magnetic fields, 
the others represent dilatations or changes per unit volume, the unit 
being 10'^ cubic centimetre. 
Field. 
Steel Tube V. 
Nickel Tube I. 
Iron Cap. 
Brass Cap. 
Nickel Cap. 
Brass Cap. 
560 
-587 
- 0"6 
-110 
-107 
500 
-42 
- 9-6 
-109 
-106 
400 
-30 
-18 
-107 
- 98 
300 
-18 
-12 
- 96 
- 89 
200 
0 
- 7-2 
- 72 
- 67 
100 
+ 7-2 
- 2*4 
- 29 
- 23 
50 
+ 3*0 
- 1-2 
- 4-5 
- 4*5 
