Observations regarding Fossil Infusoria. 18# 



great facility ; whilst the yellow beryl does not, so to speak, 

 transmit them at all, and the brown tourmaline as well as the 

 green, have the property in so slight a degree, that I have fail- 

 ed in my attempts to polarize the rays under these circumstances* 

 though I believe it might not be impossible, if thinner plates 

 were used than I had it in my power to employ. In conclud- 

 ing, I may observe, that I purpose shortly to resume the pro- 

 secution of the subject. 



Observations regarding Fossil Infusoria, communicated to the 

 Royal Academy of Sciences of Berlin, by Professor Ehren- 

 berg, on the $Hth and 30th June 1836.* 



THE proprietor of the porcelain manufactory at Pirkenhammer, 

 near Carlsbad, observed that the substance occurring in the peat- 

 bog, near Franzensbad, in Bohemia, and resembling the Kiesel- 

 guhr (a siliceous deposit), " is almost entirely composed of the co- 

 verings of some species of navicula, and seems to be the product of 

 the action of subterranean heat on the ancient submarine land." 

 Mr Fischer accompanied this notice with a specimen 2 inches 

 long, 1 inch broad, and | of an inch high, of the siliceous mass, 

 together with some specimens of the peat, requesting me to deter- 

 mine the animal form, and to publish the result. A microscopic in- 

 vestigation has confirmed the discovery of Mr Fischer; the Kiesel- 

 guhr of Franzensbad is almost entirely composed of extremely well 

 preserved naviculce, with which are also mixed some other Bacilla- 

 riae ; and the great transparency together with the purity from or- 

 ganic matter, of all the siliceous shields, renders it probable that 

 they have been purified and heaped together by an unusual degree 

 of heat. It is not probable that they belonged to the bottom of the 

 sea, for the great majority of the forms, as well according to the nu- 

 merical relations as the striping, are identical with the Navicula 

 viridis, a species found so abundantly in all the fresh water near 

 Berlin. Naviculce can also be recognised in the specimens of 

 the turf; and although for the most part different from those 

 of the Kieselguhr, have nevertheless the forms of living species. 

 An examination of original specimens of the Kieselguhr from the 

 Isle of France and Santa Fiora, in Tuscany, similar to those ana- 



f From "VViegmann's Archiv fur Naturgeschichte, Zweiter Jahrgang. 

 ViertesHeft. 1836. 



