454 A. Kendrick — Damping of Bell-magnets, etc. 



manium, probably about O'lO per cent. These authors call 

 attention to the fact that since tin and germanium belong to 

 the same chemical group they are isomorphous with one an- 

 other and suggest the probability of finding in Bolivia a 

 sulpho-stannate of silver isomorphous with argyrodite. The 

 new mineral described in this article corresponds precisely to this 

 idea. As the Freiberg argyrodite has been shown to be isomet- 

 ric, and the name canfieldite cannot therefore be applied to the 

 germanium compound, it is proposed now to transfer the name 

 to the new isomorphous tin compound. It is not probable 

 that this will cause confusion as the name as at first applied 

 was not long in use and has never been introduced into any of 

 the text-books or systems of mineralogy, and especially as it is 

 now transferred to a species which is very closely related, aud 

 should come next to argyrodite in a natural system of classifi- 

 cation. It is probable that various mixtures of argyrodite 

 Ag 8 GeS 6 and the molecule Ag 8 SnS 6 will be found and it 

 would seem best to consider this latter as the canfieldite mole- 

 cule, while the intermediate isomorphous mixtures would be 

 called argyrodite or canfieldite, according as the germanium or 

 the tin molecule predominated. 



Regarding the crystallization of the argyrodite and can- 

 fieldite from Bolivia the specimens examined by the author, 

 are apparently holohedral. The octahedron faces are equally 

 developed and have the same luster. There is, however, on 

 each of the dodecahedral faces of the canfieldite specimen a 

 distinct furrow or slight depression running in the direction of 

 the longest diagonal. This may indicate a twinning which has 

 given rise to the apparently holohedral form, or the latter may 

 of course have resulted from an equal development of positive 

 and negative tetrahedrons. 



Laboratory of Mineralogy and Petrography, 

 Sheffield Scientific School, New Haven, April, 1891. 



Art. LVII. — On the Damping of Bell-magnets and Ring- 

 magnets by surrounding copper; by Arthur Kendrick. 



This paper presents the results of some observations made 

 by the writer at various times upon the damping of bell-mag- 

 nets and ring-magnets in copper boxes with the view of ascer- 

 taining roughly the relations between magnetic moment, 

 inertia moment, and size and shape of the surrounding copper. 



The accompanying figures show at a glance the dimensions 

 of the magnets and some of the boxes used. Figures 1, 3, 4 

 and 9 show vertical and horizontal sections, fig. 2, a horizontal 



