﻿1861.] 



HECTOR ROCKY MOUNTAINS, ETC. 



405 



gold-mines worked since 1855 on Clark's Fork, half a mile north 

 of the boundary-line where it meets the Columbian River, prove 

 that the belt of auriferous country in California and Oregon is con- 

 tinuous with that of Eraser River ; and there is no reason to doubt 

 that in a short time the rugged and unexplored country which forms 

 a triangular region north of the boundary-line, and is drained by the 

 waters of the Upper Columbia and Kootanie Rivers will be overrun 

 by prospectors, and then by active gold-miners, just as the western 

 part of British Columbia has been within the last few years *. 



Age of the Terrace-deposits. — The evidence we have respecting the 

 age of the terrace-accumulations is very imperfect. There can be no 

 doubt that those occupying the valleys of the Rocky Mountains, being 

 furthest from the coast and at the greatest elevation, are the most 

 ancient, and that from the time of their deposit till now the rear- 

 rangement of the same materials has been carried on during the 

 gradual uprising of the continent. 



The shores of the intricate channels and inlets on the Pacific coast 

 of British North America, if elevated from the sea, would present but 

 slight difference from sides of the narrow valleys in the Rocky Mount- 

 ains at an altitude of 3500 feet. "Whether the continent was ever in 

 later times depressed to that extent in the mass, or whether the 

 central upheaval has been much greater than that along its margin, 

 is a consideration of great importance, and could perhaps be settled 

 by ascertaining to what altitude the terraces can be traced on the 

 Cascade Mountains. 



The existence of marine Tertiaries along the coast, supposed to be 

 of the same age as those in the eastern prairies, and also within 

 the Cascade Range at slightly greater elevation and sometimes over- 

 flowed by the lava from those mountains, would seem to indicate that 

 the elevation has been very unequal ; or, in other words, that the 

 Tertiary formations along the Pacific coast have hardly been raised 

 at all, while those in the interior are elevated several thousand feet. 



On the eastern plains we have marine and other Tertiaries at an 

 altitude of about 3000 feet above the sea, and Hayden describes 

 them as " in all cases undisturbed, and not unfrequently resting on 

 the upturned edges of azoic and granitic rocks t." But in the 

 prairies these Tertiaries, along with the Cretaceous strata on which 

 they generally repose, have been enormously denuded, and are 

 found merely as outlying patches forming the tops of hills. It must 

 have been during the period when this denudation of the eastern 

 plains accompanied the gradual emergence of the continent, but acting 

 with very different results on the rocky sea-bottom and successive 

 ranges of iron-bound coast presented by the western slope, that 

 these immense deposits of shingle were formed and moulded into 

 terracesj. 



* I have just heard that some Americans have discovered that there is gold 

 deposited by the Saskatchewan at the Rocky Mountain House. If so, it must 

 be washed out of the shingle-terraces along the eastern base of the mountains. — 

 Aug. 1, 1861. t Proc. Acad. Nat. Sci. 1858, p. 17. 



\ In many cases there is no doubt that the terrace-arrangement has been 



