( 835 ) 
men*. The method of the magnetic rise seemed in some instances to 
give a decrease of the order of 1% in a field of 8000 gauss, while 
the method of the maximum couple gave with the cylindrical pole- 
pieces up to 12000 gauss only a very small systematic deviation and 
with the conical pole-pieces (16000 gauss) the deviation was scarcely 
appreciable. 
The solid oxygen ellipsoid with which a much lower temperature 
was reached seemed to give a small decrease at 16000 gauss; it is 
possible, however, that a greater deviation is obscured by the cor¬ 
rection for the non-uniformity of the field. We consider, however, 
that, assuming that the experiments were accurate to within l*/# the 
change of the susceptibility with the field up to 16000 gauss remains 
within the limits of experimental error. This is in agreement with 
the theory of Langevin, if this, notwithstanding the deviation from 
Curie’s law, is still applied. 
Physics. — “The magneto-optic Kerr -Effect in ferromagnetic com¬ 
pounds and alloys”. By Stanislaw Lorja. (Communication 
from the Bosscha-Laboratory). 
It has been shewn by Kaz •), Righi’), Kokdt*), Sissingh-), Zeemas*) 
and also by Kerb*) himself that the phenomenon discovered by the 
last named in 1876 depends not only on the orientation of the 
reflecting surface with respect to the magnetic vectors, bnt also (in 
a somewhat complicated manner) on the angle of incidence and he 
position of the plane of polarization of the incident beam. In the 
simplest and by far the most important case of almost nornud incidence 
of light polarized perpendicularly or parallel to the plane of incidence, 
the reflated light in general is elliptically po anzed accord,.® to 
Rigbi '); the rotation of the major axis of the ellipse depends on the 
magnetisation and the wave-length. 
According to the measurements made by do Bois ) it is inevery 
ci propoHional .0 the former; as regards the variation with the 
1) P. C. Kaz, Biss., Amsterdam 1884 - 
=) A. Riem, Ann. de Cbim. at Phys. (6) 4 
») A. Kundt, Wied. Ann. S3 p. 238, 1884 ; 27 p. 199, 188b. 
;> l S’ k”895; no. 29, 1896. Arch. M 27 p. 
” iTsnn, Phi,. Mag. (5, 3 ,W ’ ^ ^ 
n A. Righi, Ann. de Chanel Phys_ ()9p. 120, -886. 
») H. DO Bois, Wied. Ann. 39 p. 25, 1890. 
