CVl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



de Geneve ' for last year a notice on the Occurrence of Gold in Cali- 

 fornia, iifter describing the different localities and formations in 

 which the gold is found, M. Marcou concludes by observing that he 

 has arrived at the same conclusion as Sir R. Murchison respecting 

 the gold of the Ural, viz. that its deposit took place betv^^een the 

 conclusion of the miocene formation and the post-pliocene or quater- 

 nary period. With this difference, however, that in California the 

 eruptive rocks in which the gold has been formed, and which are its 

 true matrix, do not belong, as in the Ural, to the Silurian system, 

 but to the miocene or pliocene period. They certainly are more 

 recent than the eocene, the beds of which they have disturbed and 

 dislocated. Moreover in California the veins of auriferous quartz were 

 formed at the same time as the eruptive rocks in which they occur, 

 and not subsequently to them as in Russia. 



Professor Henry D. Rogers has recently published, in Edinburgh, 

 a Geological Map of the United States and British North America. 

 This Map forms a portion of Keith Johnston's Physical Atlas, and has 

 been engraved by him for that work. It professes to be constructed 

 from the most recent documents and unpublished materials. It is 

 therefore with the greater surprise that I find that Prof. Rogers, 

 contrary to the opinion of the majority of his countrymen, and of the 

 officers of the Geological Survey of Canada, has entirely ignored the 

 existence of the Lower Silurian group, and has referred the rocks 

 which the American geologists designate as such to the Cambrian 

 system. I need only refer you to the able and eloquent address of 

 Prof. Dana, already alluded to, for a confirmation of the statement 

 that the division of Upper and Lower Silurian is fully recognized by 

 American geologists. In alluding, near the close of his address, to 

 the disturbances which appear to have marked on the American 

 continent the separations between various epochs. Prof. Dana ob- 

 serves — " The question of the existence of a distinct Cambrian system 

 is decided adversely by American records. The mollusca in all their 

 grand divisions appear in the Lower as well as in the Upper Silurian, 

 and the whole is equally and alike the MoUuscan or Silurian age. 

 The term Cambrian, therefore, if used for fossiliferous strata, must 

 be made subordinate to Silurian." 



In another portion of this eloquent address. Prof. Dana says, in 

 reviewing the succession of epochs in American geological history, 

 that after the close of the Azoic age, in a period of extensive meta- 

 morphic action and disturbance, the Silurian or Molluscan age 

 next opened, and continued, under various aspects and numerous sub- 

 divisions, until the commencement of the Devonian age or age of 

 fishes. Here then we have a great natural-history character by which 

 to designate the Silurian age, viz. from the first commencement of 

 molluscan life down to the period when the first vertebrate animals 

 appeared in the form of fishes. The Silurian or Molluscan age 

 is, however, distinctly divided by Prof. Dana into the Upper and 

 Lower Silurian, each of which is again subdivided into several 

 periods. 



For other evidence of the opinion of American geologists on this 



