Geological Soclelg. 139 



event produces in us little surprise; but if this were not so, we could 

 not avoid being struck with one feature of Prof. Ehrenberg's dis- 

 coveries ; — that while the microscopic contents of the more recent 

 strata are all freshwater Infusoria, those of the chalk are bodies 

 {Peridineum, Xanthidium^ Fucoides^ which must, or at least can, 

 live in the waters of the ocean. Nor has Prof. Ehrenberg been con- 

 tent with examining the rocks in which these objects occur. During 

 the last two years he has been pursuing a highly interesting series 

 of researches with the view of ascertaining in what manner these 

 vast masses of minute animals can have been accumulated. And 

 the result of his inquiries is*, that these creatures exist at present in 

 such abundance, under favourable circumstances, that the difficulty 

 disappears. In the Public Garden at Berlin he found that workmen 

 were employed for several days in removing in wheelbarrows masses 

 which consisted entirely of fossil Infusoria. He produced from the 

 living animals, in masses so large as to be expressed in pounds, tri- 

 poli and polishing slate similar to the rocks from which he had ori- 

 ginally obtained the remains of such animals ; and he declares that 

 a small rise in the price of tripoli would make it worth while to 

 manufacture it from the living animals as an article of commerce. 

 These results are only curious ; but his speculations, founded upon 

 these and similar facts, with respect to the formation of such rocks, 

 for example, polishing slate, the siliceous paste called kieselguhr, and 

 the layers of flint in chalk, are replete with geological instruction. 



As the discoveries of Prof. Ehrenberg are thus full of interest for 

 the geological speculator, so have they been the result, not of any 

 fortunate chance, but of great attainments, knowledge, and labour. 

 The author of them had made that most obscure and difficult portion 

 of natural history, the infusorial animals, his study for many years ; 

 had travelled to the shores of the Mediterranean and the Red Sea 

 in order to observe them ; and had published (in conjunction with 

 Prof. Miiller) a work far eclipsing anything which had previously 

 appeared upon the subject. It was in consequence of his being 

 thus prepared, that when his attention was called to the subject of 

 fossil Infusoria, (which was done in June, 1836, by M. Fischer) he 

 was able to produce, not loose analogies and insecure conjectures, 

 but a clear determination of many species, many of them already 

 , familiar to him, although hardly ever seen perhaps by any other eye. 

 The animals (for he has proved them to be animals, and not, as others 

 had deemed them, plants) consist, in the greater number of examples, 

 of a staff-like siliceous case, with a number of transverse markings ; 



* Abhandl. Kon. Ak. Wissensch. Berlin. 1838. 

 L 2 



