(rrolotjtj ami Mineralogy. 



rocks." Dikes intersect inn- 

 tavor the concentration of rich ore-bodies or bonanzas in their 

 vicinity;" but the planes of faults afford no deposits of import- 

 ance, and evidently for the reason that "their origin is later than 



ous sheets preceded the production of the ore-deposits and ot the 



Cretaceous, and which has continued to be followed by feeble 

 movements until the present time, even since the opening, accord- 

 ing to some evidence, of the Leadville mines. 



Mr. Emmons's abstract of Ids lieport is, like all hi- geological 

 . dear and precise in style, and of the best kind of science 



I Note o I »y Wm. H. Dall, U. S. 



Coa>t Snrvev. (Communicated in reply to a letter from J. D. 

 Dana.)— Our present knowledge of the existence of Miocene 

 deposits in northern Alaska depends on the identification by Dr. 

 Ne\c berry of certain leaf-bearing strata from Norton Sound and 

 the Yukon River. All along the coast of Alaska there is a series 

 of brown sandstones with marine fossils, which appear to be the 



ngn North Harbor. 



of Unga Sound. 



