Transactions of the Geological Society of France. 291 
plumose alum, and is six inches in thickness. It covers a stratum 
of epsom-salt, one and a half inches in thickness. The epsom- 
salt is accompanied by decomposed mineral substances and lamine 
of Mica. M. Srromeyer has detected among these foreign sub- 
stances, silica, alumina, a little iron, manganese, a little lime and mag- 
nesia, common salt, sulphate of manganese, &c. A micaceous 
quartz rock impregnated with alum and epsom-salt supports the 
whole. ‘The roof of the cave is formed in general, by a quartzose 
conglomerate containing iron pyrites, and oxide of manganese. 
In analyzing the alum of the Cape, M.Srromeyer found that it forms 
a new sub species to which he gives the name of Manganesiferous 
and Manganesian alum. He compared it with the fibrous alum 
found with lignite at Tschermig in Bohemia, because M. Ficinus 
had supposed that this also was a magnesian alum ; but his research- 
es have confirmed the results obtained by MM. Lampapius and 
Gruner, who had classed it with ammoniacal alum. 
M. Srromever found the African epsom-salt mixed with a notable 
quantity of sulphate of manganese. ‘The same chemist was induced 
by these researches to undertake anew, the analysis of certain saline 
efflorescences from Idria, Arragon, and Neusohl in Hungary. The 
Idrian salt instead of being alum, is epsom-salt. The stalactites of 
bitter salt from Hungary owe their rose red color to sulphate of cobalt, 
and contain also, sulphate of copper, of manganese and protoxide of 
copper, as well as water mechanically lodged in their cavities. The 
saline needles from Arragon are pure epsom-salt. 
M. Becaqueret has discovered methods for crystallizing in the 
humid way, the sulphurets, iodides, and bromides of the different 
metals, and particularly of the metallic oxides. 
Galena being volatile and susceptible of being obtained crystal- 
lized by sublimation, it has been inferred that this substance was for- 
med in the igneous way, in metalliferous veins. Nevertheless this 
ore is found in other situations, where the geologist would be led to 
attribute to it an aqueous origin, if chemical facts were not opposed 
toit. With his characteristic invention, M. Bequeret applied him- 
self to the question whether this substance could not be crystallized 
in the humid way. He employed for this purpose a sulphuret of 
mercury, upon which he poured a solution of the chloride of mag- 
nesium ; he introduced into the mixture a lamina of lead and closed 
up the whole hermetically in a glass tube. After the expiration of 
many months, he found that the lead had passed to the state of a sul- 
