414 Geological Memoirs. 



In this case, as before, the spiculse of sponges, which are always 

 detached and fragmentary, can neither have penetrated the volcanic 

 tuff, nor can they have been there developed in a fragmentary state, 

 while such a notion is still less tenable with respect to the infusorial 

 animalcules. A merely elevated sea-bottom which had not been 

 exposed to intense heat must necessarily have exhibited various or- 

 ganic bodies, as in Oran, Sicily and Virginia, containing entire 

 sponges, corals, foraminifera and shells, and would not merely con- 

 sist of fragments of pumice and of siliceous-shelled infusoria. Fora- 

 minifera and all other calcareous remains are here entirely absent, 

 and they, as well as the argillaceous particles on the sea-bottom, have 

 probably served partly as a flux for reducing the fused siliceous 

 particles, and have partly been decomposed to form the gypsum. 



[The author then proceeds to describe several infusorial remains occurring 

 in the loamy earth of Patagonia and the banks of the Plata, whence were 

 obtained the gigantic mammalian remains of Edentates and other animals 

 brought home by Mr. Darwin and described by Professor Owen. These are 

 almost entirely of freshwater origin, and differ therefore from those found in 

 the rock already alluded to. He next mentions two kinds of Phonolite, the 

 trass of the Siebengebirge, and the ashes under which Pompeii is buried, as 

 all containing infusorial remains, although the number of species is not con- 

 siderable ; and he concludes by alluding to a singular instance of a body 

 apparently organic but not infusorial, found in the trachyte of Zimapan in 

 Mexico. These matters not bearing directly upon the principal point in 

 question in this memoir are here omitted. — Ed.] 



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 



