266 WALKS AND TALKS. 



California. The continent eastward became an archipelago. 

 Cambrian sediments were deposited over all its scarred and 

 broken surface. One ocean stretched from western Nevada 

 to New England. Whether the Atlantic Seaboard Land rose 

 or subsided, we are unable to say. Probably it sank, and its 

 original extent became concealed by overlapping Cambrian 

 sediments. The Great Northern Land, however, began a slow 

 upward movement, which was destined to continue through 

 all Palaeozoic time. 



In the progress of the Palaeozoic ages, the tenor of conti- 

 nental history was an almost continuous emergence of the 

 Laurentian portion of the Northern Land, and a continuous 

 sinking of the Cordilleran Land. The Laurentian, accord- 

 ingly, continued to broaden its base as the remnants of the 

 Cordilleran continued to grow less. The Cordilleran sub- 

 sidence was greatest toward the shore of the Nevada conti- 

 nent, which was undergoing vast wastage in supplying the 

 sediments which overspread the surface of the sunken Cordil- 

 leran region. Coarse and thick toward the west, they became 

 finer and thinner eastward. By the close of Palaeozoic time, 

 the sediments accumulated over the Cordilleran Land were 

 one thousand feet thick in the Kocky Mountains, thirty-two 

 thousand feet in the Wahsatch region, and forty thousand 

 feet at the extreme western Palaeozoic limit, longitude 117 

 3(X west. Only a few granitic islands interrupted the con- 

 tinuity of the uppermost Carboniferous sheets, from Nevada 

 to the Great Plains. The ancient Eozoic topography was 

 buried irretrievably out of sight save where, in later times, 

 local uplifts brought it again up to observation. The Appa- 

 lachian region, meanwhile, underwent a similar subsidence. 

 There are some reasons for supposing this region was, at the 

 beginning of Palaeozoic time, annexed to the western border 

 of the Seaboard land. If so, the conditious here were a sink- 

 ing land loaded with sediments derived from a wasting stationary 

 land on the east; as in the west, the situation was the same, but 

 with the wasting land on the west. West and east the fixed 

 and wasting land was oceanward from the sinking area. 



