INTRODUCTION. 
73 
plateau of the west, we have a much greater proportion above the level 
of the sea. 
So far, therefore, as our observation extends, we are able to deduce 
some general principles in regard to the production of this mountain 
range. To explain its existence, we are to look to the original accumu¬ 
lation of matter along a certain line or zone, the direction of which 
will be the direction of the elevation. The line of the existing moun¬ 
tain chain will be the course of the original transporting current. 
The minor axes or foldings must be essentially parallel to the great 
synclinal axis and the line of accumulation. The present mountain 
barriers are but the visible evidences of the deposits upon an ancienf 
ocean bed ; while the determining causes of their elevation existed long- 
anterior to the production of the mountains themselves. At no point, nor 
along any line between the Appalachian and Rocky mountains, could the 
same forces have produced a mountain chain, because the materials of 
accumulation were insufficient; and though we may trace what appears 
to be the gradually subsiding influence of these forces, it is simply in 
these instances due to the paucity of the material upon which to 
exhibit its effects. The parallel lines of elevation, on the west of the 
Appalachians, are evidenced in gentle undulations, with the exception 
of the Cincinnati axis, which is more important, extending from Lake 
Ontario to Alabama, and is the last or most western of those parallel 
to the Appalachian chain. 
In this connection, we come now to the consideration of the important 
phenomenon of the metamorphism of strata composing a large part of 
the Appalachian range. Approaching from the west, and crossing the 
successive low parallel undulations of the strata, we find their incli¬ 
nation becoming more and more extreme. Coincident with this there 
is a gradual and almost imperceptible change in the condition of the 
strata. The shale appears as if partially crushed or pressed, and shows 
striae and smooth shining surfaces which are not parallel to the line of 
bedding : it breaks or separates into small, irregular fragments, with 
[ Palaeontology III.] 10 
