76 GEOLOGICAL MEMOIRS. 



or volcanic ashes, as well as clink -stone, and apparently the crumbling 

 niarecanite-tuft', besides the various volcanic fused and erupted rocks, 

 have one after another and in rapid succession been found to exhibit 

 a direct and necessary relation with the most minute forms of or- 

 ganic existence, and tliat such is the case from whatever part of the 

 earth these rocks are obtained. 



The progress of the investigation is as follows : — 



A specimen of very white siliceous earth of loose texture and 

 small specific gravity, obtained from the foot of the volcano ' Hoch- 

 simmer' near the lake of Laach on the Rhine, was in July 1844? for- 

 warded to the author by Prof. Noggerath of Bonn for microscopic 

 investigation, the specimen being suspected to contain infusorial 

 remains. It appeared on examination that the whole mass, with the 

 exception of a few grains of quartzose sand, consisted of siliceous 

 infusorial cases, v.'hile the peculiar association of species and their 

 diminutiveness, and especially the remarkable preponderance of Pm- 

 nularia viridula, induced the author to conclude that there existed 

 some peculiarly interesting relations of the beds ; and he expressed 

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

 spect 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 

 investigation was not satisfactory as regarded the locality, and it 

 became necessary to have the pits re-opened. The specimens hoM- 

 ever 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 in- 

 timately 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 phsBnomena 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 pro- 

 duced great disturbances and disruptions of the stratified rocks, 

 which rendered it very difficult to determine, at least during a hur- 

 ried survey, the original relations of the superficial phaenomena and 

 the date of the metamorphism. The Bilin infusorial polishing slate 

 is however clearly a stratified rock, having relation to the other for- 

 mations, 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 appa- 

 rently to the Planer-kalk, and then by about ten feet of clay con- 

 taining ironstone balls. The infusorial mass, which on the whole is 

 about fifty feet thick, surmounts this clay, and presents the appearance 

 of a mammillated slate, a polishing slate, or a semi-opal, according to 

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

 perfectly clear. The author endeavoured to find some springs of 

 water which might have produced these phaenomena in modern 



