Geology and Botany of Northern Pacific Railroad. 20* 



(i EOLOGICAL SUBSTRUCTURE. 



The sheet of drift which lias been described covers most of the 

 lowland, and conceals the underlying rocks so that they appear 

 only about the margin of the basin. The foot-hills of the Sierra, 

 like the more elevated portions, are composed chiefly of eruptive 

 rocks ; but at various places along the northern and eastern mar- 

 gin of the basin, the drainage streams have exposed sedimentary 

 strata. These are all Cretaceous or Tertiary. On Queen Char- 

 lotte's Island, as we learn from the Canadian geologists, are 

 Lower Cretaceous rocks, very much disturbed, but containing 

 beds of lignite converted into anthracite, and many mollusks 

 which apparently represent the Neocomian of the Old World. 



On Vancouver's Island, the granites and old metamorphic sed- 

 iments are succeeded by Upper Cretaceous strata, which contain 

 several valuable seams of coal that have been worked for many 

 years. Specimens of the fossil plants and mollusks associated 

 with these beds, were sent by Mr. George Gibbs to the writer in 

 1858. Among the former were Inoceramus and Baculites, which 

 gave the earliest information of the Cretaceous age of these de- 

 posits. Descriptions of some of the fossil plants were published 

 by the writer in the Proceedings of the Boston Society of Natural 

 History for 1863. On Orcas and Sucia Islands are also exposures 

 of Cretaceous rocks which abound in fossils. 



On the east side of the basin, coal outcrops at several points, 

 and has been w T orked at Bellingham Bay on the Skagit River, at 

 Newcastle, Carbonado and Wilkinson. At Carbonado the coal- 

 bearing rocks, turned up at a high angle, are cut across in a 

 canon formed by Carbon River, and a very satisfactory view is 

 here obtained of the structure of one of the local basins. The 

 series is several thousand feet in thickness ; and in this section 

 nine workable seams of coal are exposed. At Wilkinson and in 

 that vicinity, Mr. Willis made a careful exploration of another 

 basin, which also includes several beds of coal and some thous- 

 ands of feet of associated rocks. From these localities and others 

 further north, large collections of fossil plants have been made 

 by the writer and his assistant, Mr. Edward Lorrance. These 

 represent a rich and interesting flora of Upper Cretaceous and 



