590 EEPOET OF NATIONAL MUSEUM, 1904. 



he believed dry land to have prevailed over a large portion of the 

 West, and he found no evidence of deep-water deposits until far up 

 into the Cretaceous. Near the close of this epoch the waters of the 

 great Cretaceous seas receded toward the present position of the 

 Atlantic on the one side and the Pacific on the other, leaving large 

 areas in the central West dry land with but a slight elevation above 

 the sea level. He showed that the White River Tertiary deposits 

 were younger than the Lignite, and that the older members of the 

 western Tertiary were clearly separable into four divisions exclusive 

 of the Pliocene of the Niobrara. He believed that the estuarian depos- 

 its ushered in the dawn of the Tertiary epoch and that they belonged 

 to the Eocene period. The evidence of the fossils was regarded as 

 indicating that a much milder climate prevailed throughout the West 

 during the greater part of the Tertiary than at present — a climate 

 somewhat similar to that of the Gulf States at the present day. 



In an article on the Primordial sandstone of the Rocky Mountains, 

 published in the American Journal of Science for 1862, he announced 

 the finding of undoubted evidence of the existence of the equivalent 

 of the Potsdam sandstone of the New York series in two important 

 outliers of the Rocky Mountain chain. He pointed out the singular 

 uniformity in the nature of the sediments and general lithological 

 resemblance to the eastern type, but did not regard this as due to the 

 currents bringing the material from the East. He thought, rather, 

 that the uniformity was due to a similar uniformity on the part of the 

 underlying rocks from which sediments were derived — that is, he 

 believed that the source of all the sediments composing the Primor- 

 dial rocks in the West could be traced to underlying rocks in the 

 immediate vicinity. He noted the gradual thinning out of this Pri- 

 mordial sandstone toward the West, and quoted the observations of 

 D. D. Owen in Minnesota. Whitney in Iowa, Satford in Tennessee, 

 and Shumard in Texas as confirmatory. The lower secondary forma- 

 tions, on the other hand, as he pointed out, gradually increased in 

 thickness. 



He noted no unconformability in any of the fossiliferous sedimen- 

 tary rock.s of the Northwest from the Potsdam sandstone to the sum- 

 mits of the true Lignite Tertiary, but found proof of two great periods 

 of disturbance, the one prior to the deposition of Potsdam sandstone, 

 when the Azoic or granitic rocks were elevated to a more or less 

 inclined position, and the other, much the more important, at the 

 close of the Lignite Tertiary, when the "massive nuclei of the ranges 

 were raised above the surrounding country." 



In the American Journal of Science for 1862 Hayden had an impor- 

 tant paper in regard to the period of elevation of the ranges of the 

 Rocky Mountains near the sources of the Missouri River and its tribu- 

 taries. He regarded the evidence as clear that the great subterranean 



