78 GEOLOGICAL MEMOIRS. 



formation. Whether indeed the sulphates of soda and lime in the 

 water have received the excess of carbonate of iron after the forma- 

 tion of the pyrites, or whether the Gaillonella ferruginea has ab- 

 sorbed sulphuric acid given off after death by the bodies of the sili- 

 ceous-shelled animalcules, the author leaves it to other naturalists to 

 determine, but he expresses his belief that the vast multitude of mi- 

 croscopic animalcules at Franzensbad have had a direct and import- 

 ant influence on the local peculiarities observed in that neighbour- 

 hood. 



By such investigations the volcano in the neighbourhood came to 

 be viewed in a new light. It rises from the plain with a gentle in- 

 clination on the eastern side, but to the west there is a nucleus of 

 cellular basalt or basaltic lava-slag rising to the summit ; the forma- 

 tion in the neighbourhood is mica-slate. The whole of the eastern 

 dome-shaped slope forms a stratified heap of light volcanic erupted 

 ashes, often containing lumps of some size and also very small frag- 

 ments of mica-slate, quartz, or white pumice. The impression made 

 by viewing these phaenomena was, that the eruptions of cellular lava 

 and slag, and consequently the whole slope of the hill, consisted of 

 nothing more than a valley or the bed of a lake of volcanic origin, 

 which existed before the outburst of lava, but that the valley was 

 not destroyed by the eruption, and received no elevation. Several 

 experiments were made with a view of confirming this impression, 

 and with regard to the stratification of the ashes it appeared not 

 necessary to assume any subaqueous action and subsequent eleva- 

 tion, or any subsequent covering by water, since they most resem- 

 bled the great rubbish heaps near Cahira in Egypt and elsewhere, 

 which exhibit the same appearance of regular stratification, and 

 have been formed without water. 



The idea therefore of a relation between volcanic action and the 

 conditions of existence of the most minute organic beings ceased to 

 be a mere vague speculation, and some proof of its correctness was 

 presented by gradual successive steps in investigation. 



On his return from his summer excursion, the author found an 

 admirable and systematic collection from his correspondent at Bonn. 

 The first glance of these under the microscope showed their nature, 

 and the investigations at Hochsimmer have gradually led to the fol- 

 lowing results. 



The infusorial polishing slate occurs on the eastern slope of the 

 Hochsimmer (about four miles from the Laacher-See), between the 

 roads which branch off" from Ettringen to St. Johann and Waldesch. 

 It is interstratified between beds of pumiceous conglomerate. 



Immediately under the vegetable soil we find- 

 feet, in. 



1. Ferruginous pumiceous conglomerate .... 8-10 



2. Volcanic tuff" 1 



3. Infusorial stratum (polishing slate) 2-3 



4. Finely-grained pumice conglomerate 2-3 



5. Coarse pumiceous conglomerate which has 



been penetrated to a depth of. 3 6 



Total thickness. . 12 ft. 4 to 15 ft. 



