Ehrenberg on Infusoria in Igneous Rocks. 397 



some peculiarly interesting relations of the beds ; and he expressed 

 a wish that a strict local investigation might be carried on with 

 respect to some at least of the peculiar species obtained. M. Nog- 

 gerath at once undertook to do this, and in the month of August the 

 author received specimens obtained from M. Spenler of Mayen, but 

 the original pits were at that time filled up, so that this first investi- 

 gation was not satisfactory as regarded the locality, and it became 

 necessary to have the pits re-opened. The specimens however which 

 were forwarded were such as to induce the author to wish for a yet 

 further investigation concerning the local relations, since in some 

 of them the infusorial earth appeared to be most intimately and 

 strikingly mingled with volcanic tuff. 



In the months of August and September his investigations on 

 these rocks were for a time suspended during a journey made by the 

 author into Bohemia, where he had the opportunity of observing 

 similar phsenomena in the field and on a grander scale. 



On this occasion he examined the vicinity of Bilin in company 

 with Dr. Reuss, and found that volcanic action had there produced 

 great disturbances and disruptions of the stratified rocks, which ren- 

 dered it very difficult to determine, at least during a hurried survey, 

 the original relations of the superficial pheenomena and the date of 

 the metamorphism. The Bilin infusorial polishing slate is however 

 clearly a stratified rock, having relation to the other formations, for it 

 is seen at the top of the Kutschliner mountain, whose principal 

 mass is gneiss, and which is surmounted first by a thickness of about 

 twenty-five fathoms of a cretaceous marl belonging apparently to the 

 Planer-kalk, and then by about ten feet of clay containing ironstone 

 balls. The infusorial mass, which on the whole is about fifty feet 

 thick, surmounts this clay, and presents the appearance of a mam- 

 millated slate, a polishing slate, or a semi-opal, according to its 

 degree of hardness. Dr. Reuss' sections have rendered all this 

 perfectly clear. The author endeavoured to find some springs of 

 water which might have produced these phsenomena in modern 

 times, but there was no trace of a spring on the bare barren summit, 

 nor could any channel be discovered on the declivity down which 

 such spring might have poured. But the amphitheatre which the 

 form of this isolated hill presented was extremely striking. Many 



