446 Intelligence and Miscellaneous Articles, 



Next follows an experimental investigation of transparent films 

 of cobalt and nickel prepared galvanoplastically. These, as was 

 discovered by Kundt in 1884, rotate the plane of polarization of 

 transmitted radiations when placed equatorially in a magnetic 

 field. No residual rotation, corresponding to any residual mag- 

 netism on the suppression of the magnetizing field, could be detected. 



The rotation was found by Kuudt to be proportional to the 

 thickness in the case of iron ; as was to be expected, this was 

 verified for cobalt and nickel. 



The maximum " twist " (i. e. rotation per unit thickness) occur- 

 ring in a field of infinite intensity was found to be, for red light : — 



In Nickel 89000° per centimetre. 



In Cobalt 198000° per centimetre. 



Iron (Kundt) 209000° per centimetre. 



The curves obtained by Kundt, in which the rotation in iron 

 films is plotted as a function of the field which magnetizes them, 

 were also experimentally determined for cobalt aud nickel. 



For all three metals it was found that these experimental curves 

 have ordinates proportional to those of the magnetic curves above 

 illustrated, the abscissa of the singular point being always the 

 same for a given metal ; proportionality existing within the limits 

 of experimental error and due regard being paid to the difference 

 in chemical and physical constitution of Rowland's material and 

 the electrolysed films employed. 



The magnetic rotation is therefore directly proportional to the 

 magnetization 3. — Wiedemann's Annalen, vol. xxxi. p. 941 (1887). 



ON THE SOLIDIFICATION OF LIQUIDS BY PRESSURE. 

 BY E.-H. AMAGAT. 



Theoretically, the hypothesis of J. Thomson enables us to pre- 

 dict that, at a given temperature, the solidification of a body will 

 be possible under a sufficient pressure, on condition that its density 

 be greater in the solid than in the liquid state. 



It has been verified, for ice by Sir W. Thomson and by Mousson, 

 and for various solid bodies by Bunsen, Hopkins, and, recently, 

 by M. Batelli ; but no example is known of liquids properly so- 

 called which have been reduced to the solid state by pressure alone, 

 even among those which are very readily solidified by cold, such, 

 for example, as benzene. 



In my researches on the expansion and compressibility of liquids, 

 I have examined, between 0° and 50° and at pressures increasing to 

 above 3000 atmospheres, a fairly large number of substances be- 

 longing either to inorganic or to organic chemistry. None of these 

 had shown signs of solidification, when the idea struck me to 

 examine bichloride of carbon (C a Cl 4 ). In my first trials, I was 



