320 J.D. Dana on American Geological History. 
and Lower Silurian,—another proof of the violence that closed 
the Lower Silurian era.* 
of an agency of inconceivable power, pressing forward from 
' * This Eastern border of the American continent, then in process of formation 
over the present Appalachian region from Labrador and Canada southwestward, la: 
deeper to the south than to the north. In 0 ; 
York, there was Jand out of water, forming its: northern limit. From: thence. it 
its natural course would haye been southwest over the Appalachian region, W in 
the s and shales were extensively accumulated; and therefore its aid i 
making these deposits can scarcely be doubted. ; 6 
_ F It is urged b Prof. Hall and others that the Carboniferous beds in the west lie 
unconformably on the beds below. But the disturbance indicated was not one 
bold flexures or uplifts, yo 
MiP. nh 
Sate : t 
. See 
anada and the Azoic of Ni orthern New. 
a, 
