MICROSCOPICAL OBJECTS IN THE POTASH SALTS. 139 



red heat, except tliat during tlic operation tliey assume a black 

 hue. In addition to these forms are to be seen certain yellow 

 crystals, of glassy clearness and of remarkable beauty ; the nature 

 of -which has never yet been satisfactorily made out. Their 

 principal constituent is likewise oxide of iron — at an earlier 

 period they were called chrysolites — nevertheless, they have 

 nothing in common with peroxide of iron, for both their shape and 

 colour are changed when heated to redness. The larger crystals 

 are precipitated when the Carnallit is held in solution ; the smaller 

 float on the surface. In the interior are to be seen peculiar 

 markings, as though organisms were enclosed in them. 



Now let that portion of the residuum which is insoluble in 

 water be further treated with acids ; it also is dissolved by re- 

 peated boiling, leaving only a small residual mass. It con- 

 tains for the most part quartz crystals, remarkable for the 

 perfection of their form and the beautiful manner in which 

 they polarise. More rarely pyrites is discovered ; at least, the 

 smaller crystals correspond with it in colour and appearance. 

 Still more rarely are seen lovely, colourless, highly refractive 

 octahedra, reminding one of diamonds ; but a long-continued 

 treatment with acids proves them to be not insoluble. G, C. 

 Kindt, of Bremen, who has done so much for the microscopic 

 world of Stassfurt, is convinced that they are referable to boracite. 



Besides these crystalline forms, a fibrous texture is met with, 

 closely interwoven with the crystals themselves, the origin of 

 which is undoubtedly organic. This fibrous matter is best ob- 

 tained by repeated washing of the flakes, which ascend to the 

 surface while the Carnallit is being dissolved. 



I have already spoken of the delicate matted threads which 

 were at one time assigned to the genus Hygroci^ocis, but which 

 appear to be identical with peroxide of iron. In this spongelike, 

 membranous mass are scattered here and there elongated, cylin- 

 drical, partially branched filaments, of a white colour, and furnished 

 with distinct cells — a circumstance which is infallible evidence of 

 their organic origin. 



The Rock Salt Formation of Wicliczka, referred to the Miocene 

 period, has, as is well known, a fossil fauna of its own — mollusca, 

 foraminifera, and ostracoda. These creatures were enabled to carry 

 on life, because the alkaline salts were periodically washed away by 

 fresh water, and on the whole the saline constituents of the element 



