THE INFUSOKIAL DEPOSITS. 



221 



# 



the Des Chutes River, which were obtained from a deposit of great thick- 

 ness, associated with volcanic rocks and found to be very rich in organic 

 forms. The frequent occurrence of infusoria in connection with volcanic 

 overflows and formation of various kinds — as, for instance, in the motja or 

 volcanic mud of the Andes — had already excited considerable attention, and 

 there was not a little discussion as to the meaning of this, at first sight, 

 seemingly strange association. The attention of Ehrcnbcrg, which had been 

 repeatedly called to this remarkable association by specimens sent from 

 various parts of the world, was especially aroused by an extensive collection 

 of material furnished by Castillo from Mexico. These were chiefly obtained 

 by means of Artesian borings, which had been executed in and about the 

 city of Mexico. The results of the investigation of this material were pub- 

 lished in the Memoirs of the Berlin Academy. 



The examination by the California Geological Survey of various portions 

 of the Pacific coast from Mexico to British Columbia brought together a con- 

 siderable number of facts and a good deal of material from various localities 

 of infusorial rocks. Those specimens collected which seemed from their ap- 

 pearance likely to contain microscopic organic forms underwent a prelimi- 

 nary examination at the hands of Professor Brewer and the writer, but most 

 of them were forwarded to Mr. A. M. Edwards, at that time residing in New 

 York and professing to make a special study of this class of subjects. Several 

 years having elapsed without any report having been received from him, a 

 duplicate series was sent to Ehrenberg, — this was in 1870, ■ — and by the aid 

 of this series and the specimens sent by the Fortieth Parallel Survey he was 

 placed in a position to acquire a quite thorough knowledge of the organic 

 forms enclosed in these deposits. 



The writer of this volume, perceiving that the nature of the connection 

 between the volcanic formations and the infusorial strata which they enclose 

 had not been fully comprehended, published an article on this subject in 

 1867.f This article was in considerable part translated and made the basis 

 of a communication by Ehrenberg in the Memoirs of the Berlin Academy,! 



* Under the title of " Ueber machine Gebirgs-Schiehten vorherrschend aus mikrosMopischen Bacilla- 

 rien bestehend, unter unci bei der Stadt Mexiko." Abhaiullungen der phys. Klasse der Konigl. Akade- 

 mte der Wissenschaften, 1869. 



t On the Fresh Water Infusorial Deposits of the Pacific Coast, and their Connection with the Volcanic 





Rocks. Proceedings of the California Academy of Science, Vol. III. p. 319. 



% Abhandlungen der Konigl Akademie der Wissenschaften, 1870. The title of the communication is 

 " Ueber die wachsende Kenntniss des unsichtbaren Lebens als felsbildcnde Bacillarien in Catifornien." 



