AMERICA THE OLD WORLD. 
27 
which those of the succeeding one collected, so 
that we have their whole sequence before us. In 
regions where all the geological deposits, Silu- 
rian, Devonian, Carboniferous, Permian, Trias- 
sic, etc., are piled one upon another, and we can 
get a glimpse of their internal relations only 
where some rent has laid them open, or where 
their ragged edges, worn away by the abrad- 
ing action of external influences, expose to view 
their successive layers, it must, of course, be 
more difficult to follow their connection. For 
this reason the American continent offers facil- 
ities to the geologist denied to him in the so- 
called Old World, where the earlier deposits are 
comparatively hidden, and the broken character 
of the land, intersected by mountains in every 
direction, renders his investigation still more dif- 
ficult. Of course, when I speak of the geological 
deposits as so completely unveiled to us here, I 
do not forget the sheet of drift which covers the 
continent from North to South, and which we 
shall discuss hereafter, when I reach that part of 
my subject. But the drift is only a superficial 
and recent addition to the soil, resting loosely 
above the other geological deposits, and arising, 
as we shall see, from very different causes. 
In this article I have intended to limit myself 
to a general sketch of the formation of the Lau- 
rentian Hills with the Azoic stratified beds rest 
