( 837 ) 
prepared, by Hilpert 1 ), presented an interesting field of research. In 
all these cases, the chemical structure resembles that of ferroferrite 
(ferroso-ferric oxide), in that the iron sesquioxide plays the acidic 
part, thus imparting ferromagnetic properties to the compound. Of 
this class of substances however, only cupriferrite and calciumferrite 
could be obtained in a state suitable for my experiments. Secondly, 
certain alloys of more or less ferromagnetic metals, and in particular 
those of nickel-iron 2 ), together with the well-known ternary Heusler 
alloy, and Wedekind’s *) binary manganese-antimony alloy present 
considerable interest. So far as I am aware, the magneto-optic pro¬ 
perties of these alloys have been only partially investigated, the only 
account of similar experiments, which I have come across, being 
Ingersoll’s communication previously referred to and a Russian paper 
by Tokmatschew 4 ), who described experiments with Hedsler’s alloy. 
I have studied the magneto-optic properties of the above mentioned 
bodies and also those of the well-known magnetic chromic oxide. 
Below an account of the preliminary results of my research is given. 
Experimental Arrangement. Solar rays were exclnst- 
vely used ; they passed through a direct-vision monochromatic tllmm- 
nator *), with divergence 1:4, thus furnishing light g™ at ,nle "^' 
The rays passed .(Fig. 1) through a lens (h) a total f 
(P), a Lippich’s arrangement of two halfshade N,cols M 
falling nearly normal on a mirror between t e wo p 
The obrervalions were earned <mt J”*! ^was 
Righi 7 ) found, that up to an angi 
- u m fipc 42 D 2248, 1909. Verb, deutsch. Phys. 
1) s. Hilpert. Ber. deutsch. Chem. Ges. 4* p. 
Ges. 11 p. 293, 1909. Paris lg98 . 
2 ) Ch. Ed. Guillaume, Les aciers au me , K . Honda, Ann. d. 
*) E. Wedekind, Ztschr. f. phys. Chem. 66 p. , 
Phys. 32, 1910. Dhvs -chem. Ges., 42 (phys. T.) p.l&, 1910 
4 ) S. Tokmatschew, Journ. d. russ. P J • 1909. 
‘> H. DU Bots, Verb. d. D. Phys. m ^ taed is given b, H-nuBoa, 
•) A description of the analyser and polanser me 
Wied. Ann. 46, p. 545, 1892. 120 , 132> 18 86- 
7) A. Righi, Ann. de chin, et de phys. W » PP 
