EHRENBERCx ON INFUSORIA IN IGNEOUS ROCKS. 89 



Sketch of the general results of these investigations. 



1. The recent varied and careful researches have confirmed the 

 notion that there exists on the Rhine, in districts marked by vol- 

 canic action, a very intimate and general relation between organic 

 life in its most minute form and the results of volcanic activity. 

 Crystals of volcanic origin, either pyroxene (augite), sodalite or 

 leucite, are mixed up directly and intimately with the fused frag- 

 ments of freshwater infusorial remains in rocks the thickness of 

 which amounts to nearly 200 feet. 



2. On the volcanic island of Ascension in the middle of the At- 

 lantic, which is singularly barren of life, being entirely without 

 trees and almost without water, there exists a considerable deposit 

 of volcanic ashes, which according to microscopic analysis is clearly 

 shown to be made up exclusively of organic bodies, most of them 

 the siliceous parts of plants, but some of them the remains of infu- 

 sorial animalcules; and these are not species inhabiting the sea, but 

 are, without exception, confined to fresh water. 



3. According to the result of numerous observations made with 

 reference to various localities in Europe, Asia, Africa and America, 

 it appeared that the relation of microscopic organic bodies to vol- 

 canic rocks was strictly confined to those forms known only as ex- 

 isting in fresh water, and it seems also, as stated above, that this is 

 the case in the island of Ascension, under very striking circumstances. 

 This might have been supposed to arise from the similar marine 

 forms not having been yet observed, or from the mixture of other 

 material at the sea-bottom having rendered the whole more readily 

 fusible, and so not presenting the phse.nomenon for investigation. 

 There has now, however, been found a volcanic formation of infu- 

 sorial tuff forming mountain masses in Patagonia, and exhibiting 

 distinctly its marine origin, so that this remarkable appearance of 

 an exclusively freshwater origin is taken away, and the marine forms 

 are fully represented. 



4. In Patagonia this Pyrohiolite rock is developed into a terrace- 

 shaped formation upwards of 800 feet high, greatly resembling the 

 European chalk, although without any trace of carbonate of lime, 

 and containing here and there a considerable quantity of gypsum. 

 It forms apparently one of the largest uniform masses of rock 

 that we know of on the earth, amongst those manifestly due to the 

 same agency throughout and perfectly continuous, and it exhibits 

 everywhere, and is perhaps chiefly derived from, the influence of the 

 most minute forms of organic existence, 



5. The Patagonian white tuff, formed perhaps during the sub- 

 marine eruptions of the great Chilian and Patagonian (vordillcras of 

 the south-western part of South America, and possibly the result 

 of the great and uniform activity of the eruptive forces which ele- 

 vated that chain of mountains, must be of tertiary or yet newer date, 

 since the pyrobiolite rock reposes on fossiliferous tertiary strata. 

 It would not be unimportant to subject to careful microscopic in- 



VOL. II. — PART II. I 



