228 J.D. Dana on the Appalachian and Rocky Mountains 
curring in the Mississippi basin, it is probable, as suggested 
elsewhere by the writer, that the epoch of uplift and disturbance 
ad its commencement even before the Permian peri 
e 
era preceding it. No raising of mountains is known to have 
occurred in North America between the Devonian and Silurian 
ages ; and only some limited uplifts and disturbances between 
Devonian and Carboniferous. The only elevations of prominent 
importance during these ages, of which we have evidence, 0c 
curred either at the close of the Lower Silurian or earlier. The 
Green Mountains, one portion of the Appalachians, date their 
first emergence, probably, from the close of the Lower Silurian. 
With a few small exceptions, therefore, the long era fromthe 
Zoic to the termination of the Carboniferous age was, com 
paratively, one of prolonged quiet, in which oscillations of level 
were in progress over continental areas, but no profound ané 
extensive disturbances. These oscillations throughout the Fale 
ozoic, had been, moreover, most profound along the Appalachi 
times the thickness acquired in the interior regi 
: +7 
region—the 
y preparatory for that making of the mountains whieh 
was to commence when Paleozoic time should draw to a close. 
