EHRENBERG ON INFUSORIA IN IGNEOUS ROCKS. 81 



contain imperfectly carbonized vegetable remains, or, in the case of 

 more complete fusion, exhibit similar forms imbedded in pumice or 

 tuff. With regard to the peculiar change produced by fusion, it 

 does not seem possible that the effect can have resulted in any other 

 way, or by foreign organic bodies penetrating the rock while moist, 

 and soon after its formation, since the appearance is peculiar, and 

 can be brought about by artificial means. 



4'. Organic remains have not been met with in all kinds of pu- 

 mice ; and only those appear to have been formed out of the infu- 

 sorial cases where there has been no powerful flux present to reduce 

 the mixture to the condition of glass. It will require further inves- 

 tigation to determine the relation of Obsidian to these pumiceous 

 formations. 



5. In the vicinity of many volcanoes which either have erupted 

 or do erupt chiefly pumice, there are great deposits of infusorial 

 animalcules, which under the names of porcelain earth, volcanic 

 ashes, siliceous sinter, polishing slate, mammillated slate, semi-opal 

 and decomposed porphyry, have been considered, and generally 

 without sufficient reason, as having a direct relation to the volcano. 

 Such is the case in the Isle of France and the Isle of Bourbon with 

 the porcelain earth and volcanic ash ; and also near Cassel, near 

 Cayssal in the Puy-de-D6me and in the Caucasus, and is recognised 

 again in the case of the polishing slate near Bilin, where the polishing 

 and mammillated slate and semi-opal are found, and at Arequipa in 

 Peru with the rock described (but falsely) as decomposed porphyry. 

 Other similar deposits however, as for instance that at Luzon near 

 Manilla, that near Mexico, and those near Eger and Franzensbad, 

 appear to have no reference to volcanic action ; and to this class also 

 belongs the recently discovered polishing slate of the Laacher-See. 



Of the infusorial deposits however, which are distinctly the result 

 of volcanic activity, and have sometimes been brought up and erupted 

 from great depths, we have several examples: — 1st, that of Iloch- 

 simmer near the Laacher-See (perhaps not erupted, and only exposed 

 to the action of heat); 2ndly, the trass of the Brohl Valley (supposed 

 by those on the spot to be the site of an ancient volcanic eruption), 

 and the similar beds from Lummerfeld ; 3rdly, the tuff of Civita 

 Vecchia near Rome ; 4thly, the pumice of Tollo, near Santiago in 

 Chili, belonging to the Maipu volcano ; 5thly, the pumice from 

 Kammerbiihl near Eger ; 6thly, the marecanite tuff near Okhotsk ; 

 and also, Vthly, the same rock at Moya near Quito. 



6. At Hochsimmer there is also a formation resembling phono- 

 lite, the component parts of which have the closest relation with 

 siliceous-shelled animalcules. 



7. It is extremely remarkable, that in all the various instances, 

 whether in Europe, Africa, Asia or America, in which microscopic 

 organic bodies are seen to exist in direct or approximate relation to 

 extinct or active volcanic action, all of these belong exclusively to 

 freshwater formations*. 



* In the subsequent part of this article it will be seen that an exception to this 

 has been found. 



