314 Intelligence and Miscellaneous Articles. 



stratification &c. is preserved. A few grains of peridote now begin 

 to make their appearance, chiefly as inclusions within the calcite 

 crystals, and thus by degrees the results already recorded are 

 effected. In the early stages only is the metamorphism selective. 

 The order in which the new minerals seem to develop is the fol- 

 lowing : — 



(1) Peridote, Periclase, Humite. 



(2) Spinel, Mica, Fluorite, Galena, Pyrites, Wollastonite. 



(3) Garnet, Idocrase, Nepheline, Sodalite, Felspar. 



Many of these minerals are crowded with microliths, which there 

 is reason to believe consist of pyroxene. 



XXXV. Intelligence and Miscellaneous Articles. 



SUSCEPTIBILITY AND VERDET'S CONSTANT OF LIQUIDS. 

 BY H. E. J. G. DU BOIS. 

 HPHIS investigation, carried out in the physical institute of Stras- 

 -*- burg University, had for its principal object to decide whether 

 the two " constants " above mentioned are really constant within a 

 considerable range of magnetizing forces ; Silow, Schuhmeister, and 

 Quincke, on the one hand, Stscheglajeff, on the other, having found 

 variations of the susceptibility and of Verdet's constant respectively. 



The magnetic measurements were made by Quincke's second 

 manometric method* ; an apparatus being specially constructed in 

 order to exactly set the manometer's narrow tube to any given 

 angle with the horizon. When this angle is made very small, say 

 30', quantitative measurement becomes somewhat difficult ; but the 

 method then affords an excellent qualitative test. When the dif- 

 ference in susceptibility of the liquid and the adjoining gas is but 

 one ten-thousandth of the susceptibilitv of water, it may still be 

 detected by this method, first used by Quet and Verdet, and quite 

 recently developed by Toepler and Hennig. The space above the 

 liquid was not generally evacuated, but filled with coal-gas or car- 

 bonic acid, whose susceptibility may be neglected. By substituting 

 oxygen for the gas, always keeping the same liquid, the suscepti- 

 bility of the former may be measured in terms of that of the liquid. 



The field between the poles of the large electromagnet used was 

 measured by means of Leduc's magnetometer t, based on Lipp- 

 mann's mercurial galvanometer. 



A Lippich's polarizer was used to determine the rotation of the 

 plane of polarization. 



The following is a summary of the results obtained : — 



The susceptibility and Verdet's constant for all simple liquids, 

 salts in solution, and gases, appear to be constant for magnetizing 



* Quincke, Wied. Ann. vol. xxiv. p. 374 (1885). 

 t Leduc, Journ. de Phys. [2] vol. vi. p. 184 (1887) 



