20(5 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



and those north and south of the great valley of the State. Dr. White 

 and I therefore visited Oregon and made several trips into the mountains 

 of the Cascade Range from Roseburg. 



The sedimentary rocks appear to be underlain by granite, for, though 

 we did not meet with this rock in place, it constitutes a large proportion of 

 the stream pebbles. It is stated on the excellent authority of Rev. Thomas 

 Condon to occur in place somewhat to the northward of this point. In 

 a great number of localities we found upturned, crumpled, silicified, and 

 metamorphosed rocks exactly similar to those of Mt. Diablo, but our search 

 for Aucella. was not rewarded. Upon the metamorphic rocks lie uncon- 

 formably somewhat tilted, unaltered sandstones. These are certainl}' Mio- 

 cene, for, though we found no fossils ourselves. Dr. White examined ex- 

 tensive collections of Miocene shells in entirel}' similar rock made by 

 Rev. Thomas Condon, who gave us full information as to their occurrence 

 in precisel}' similar positions, but somewhat north of Roseburg. Overlying 

 the sandstones are large areas of volcanic rocks.^ 



In the section made by the Columbia River no metamorphic rock or 

 granite appears, but at least the southern portion of the range has a foun- 

 dation similar to that of the California Coast Ranges, and, as I think, prob- 

 ably of the same age. This cannot be stated as a certainty until Aucella 

 has been found in the Cascades; but, considering that this fossil certainly 

 occurs near Puget Sound and that the lithological character and geological 

 association of the metamorpliic rocks at Roseburg are indistingui.shable 

 from those of known Neocomian localities in the Coast Ranges, no grave 

 doubt remains. 



Chico beds, liowever, occur in central Oregon, and on this ground the 

 Blue MountQ-ins have been regarded as the northerly contiiuuition of the 

 Sierra.^ Butshore lines and lines of structure, though intimately associated, 

 do not always coincide. A depression of only 30 feet to-day would put 

 Sacramento, Stockton, and an immense area of the Great Valley under 

 water, while a depression of 400' feet would convert the Great Valley into 



' In auswer to an inquiiy, Prof. Joseph Le Coute states that bis remarks couceiuing the lower por- 

 tion of tlie Cascade Range in Am. Jour. Sei., 3il series, vol. 7, p. 177, were not from personal ohserva- 

 tion. He there suggested that the Cascades were a continuation of the Sierra. 



- U. S. Geol. Expl. 40th Parallel, Systematic Geology, vol. 1, p. 453. 



