9 
Ordinary Meeting, November 2nd, 1886. 
Professor OsBORNE Reynolds, LL.D,, F.R.S., Vice-President, 
in the Chair. 
“Measurements of the Magnetic Induction and Perme- 
ability in Soft Iron,” by H. Holden, B.Sc., communicated 
by Dr. A. Schuster, F.R.S. 
As absolute determinations of the temporary and per- 
manent magnetic induction in rings have, I believe, been 
published by Rowland only, it was thought desirable to 
make a few experiments with iron rings, which were pre- 
pared in a different and, it is thought, better manner. These 
experiments were conducted during the summer vacation in 
the Physical Laboratory of the Owens College, under the 
superintendence of the Demonstrator, W. H. H. Gee, B.Sc. 
Rowland says,^ “In selecting the iron, care must be used 
to obtain a homogeneous bar : in the case of a ring I believe 
it is better to have it welded than forged solid ; it should be 
then well annealed, and afterwards have the outside taken 
off all round to about Jin. deep in a lathe.” In general, 
absolute measurements of magnetic induction and perme- 
ability in soft iron have been made by means of welded 
rings. It seems to be, at least, doubtful whether a ring 
prepared in this manner is magnetically homogeneous 
throughout, especially at the weld. 
The ring, with which the results given below were ob- 
tained, was made by cutting a disc about fin. thick from 
* Phil. Mag., Vol. XLVI., p. 149, 1873. 
PROCEEDiNas— L it. & Phil. Soc.— Vol, XXVI.— No, 2.— Session 1886-7 
