EXTRACTS FROM FOREIGN SCIENTIFIC JOURNALS. 



Geological. 



Upon Fossil Infusoria, by C. G. Ehrenberg. 



M. C. Fischer, the proprietor of the manufactory of porcelain at Pirkenham- 

 mer, near Carlsbad, has observed that the substance resembling siliceous concrete 

 ( Kieselguhr ) , which occurs in the peat bogs near Franzensbad, in Bohemia, 

 " consists almost exclusively of the cases of several species of Navicular, and ap- 

 pears to be the fire-proof remains of the (in parts) intensely heated bottom of the 

 ocean." 



Together with this information M. Fischer sent me a piece of the siliceous 

 mass about 2" long, 1" broad, and |" high, as well as some specimens of the peat, 

 intreating me to ascertain the animal and to publish the result. Microscopic in- 

 spection immediately confirmed the discovery of M. Fischer, that the siliceous 

 concrete (Kieselguhr J of Franzensbad consisted almost exclusively of very well 

 preserved Naviculce, with which some Bacillariee were intermixed, and the per- 

 fect transparency of their siliceous cases and their freedom from all organic matter, 

 renders it probable that an unusually intense heat had purified them and amassed 

 them together. It is not likely that they should have originated at the bottom of 

 the sea, for the majority of the animals both in form and the relative numbers of their 

 striae correspond very accurately with those of the Nav. viridis, which is found in 

 all the fresh water about Berlin as well as elsewhere. In the specimens of peat I 

 could also recognise Naviculce, yet they were generally different, although still ex- 

 isting species, fewer in relative proportion, and the prevailing forms very dissimilar. 



Original specimens of the siliceous concrete (Kieselguhr) of the Isle of 

 France, and of Santa Fiora, in Tuscany, which were analyzed by Klaproth, shewed 

 that they likewise consisted almost exclusively of the envelopes of Infusoria of 

 several genera of Bacillariee, yet sometimes of the same, and almost all still living, 

 species, in conjunction with rare siliceous spicula of fresh and sea- water sponges, 

 without any intervenient binding material. This, therefore, is an additional con- 

 firmation of Kiitzing's discovery that the cases of the Bacillariee consist of silica. 



I myself discovered, several years ago, that the ochraceous slimy substance, 

 which sometimes covers the bottom of marshy brooks and moats, and which ap- 

 pears to have been considered as a deposit of the oxyde of iron, is a very delicate 

 Bacillaria, which at a red heat becomes red like the oxyde of iron, and is very fer- 

 ruginous, but which does not lose its form either by a red heat or upon being treated 

 with acids, and consequently possesses a siliceous case most approaching to that of 

 the genus Gaillonella. I therefore figured it last year, as Gaillonella ferruginea 

 in plate 10 of my Infusorien Codex, which will now soon appear. All the ochre 



