﻿406 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Apr. 10, 



But if this reasoning is to apply to the most ancient of those 

 accumulations, and so place them as more recent than the latest 

 Tertiary times, then there must have been a slight depression prior to 

 the steady and gradual elevation of the continent that has continued 

 ever since. Moreover, unless this depression was local and confined 

 to the mountain-region, how are we to account for the absence of 

 Post-tertiary formations over the high-lying Tertiaries of the plains 

 in sufficient quantity to have allowed time for the production of such 

 a gigantic formation of waterworn stones ? 



On the other hand it is possible that their production may have 

 commenced in Tertiary times, so that they are almost coeval with 

 the great lignite-basin of the Missouri, which is an estuarine de- 

 posit resting, according to Hayden, quite conformably on his Upper 

 Cretaceous beds. 



He also describes his Titanotherium-bed, the lowest of the White 

 Eiver Tertiary basin, which has yielded so many forms of chelonian 

 and mammalian remains, as likewise resting without a break of con- 

 formity on the Upper Cretaceous*. Thus if this latter suggestion 

 respecting the age of the most ancient of the terraces be correct, 

 they must have been formed in the straits and inlets of an archipe- 

 lago or rocky reef lying to the west of a flat Cretaceous continent, 

 in which were estuaries and lagoons choking with rank vegetation, 

 and large lakes, which gradually filled up, burying the remains of 

 the gigantic turtles and extinct forms of mammals. 



In the Gulf of Georgia there are beds of conglomerate and coarse 

 sandstone overlying the Cretaceous strata to all appearance, and 

 which, I have thought, may perhaps correspond to the more ancient 

 of the mountain-terraces to which they bear a great mineral resem- 

 blance, excepting that those in the Gulf of Georgia have been much 

 disturbed, so that they are harder and their bedding is better marked. 

 The difference is, however, not greater than we should expect, if we 

 consider the one group to have been placidly raised to a great 

 altitude, while on the other the force has been expended in producing 

 plications and faults. 



Drift of Pacific Coast. — The glacial markings on the metamorphic 

 rocks of Vancouver Island are better displayed than I have elsewhere 

 seen them. Every surface near Victoria that is either naturally 

 exposed, or from which the soil has been removed, exhibits deep 

 parallel furrows, generally with a N.E. trend. They are also seen on 

 the main land at the entrance to Puget Sound quite as distinctly. 

 Erratics are distributed all along the Pacific coast, at least as far 

 south as latitude 46° N., where they occur, but not very plentifully, 

 near Vancouver and in the valley of the Willamette. They are 

 often of great size, and on Vancouver Island are composed of a grey 



given to these deposits by the shore-line-action of lakes which formerly occupied 

 the irregularities of the surface of the country ; but we can hardly suppose that 

 the material itself, consisting of smoothly worn fragments of the hardest rocks, 

 could have been entirely the result of the feeble erosive agencies that such lakes 

 exercise. 



* Troc. Acad. Nat. Sci. 1858, p. 10. 



