J. LeConte—Formation of the Karth-surface. 451 
result has been much confusion of thought. For it is evident 
that the great bulge which constitutes a snountain chain, and 
which can be seen only from a distance, is formed in an entirely 
different way from the smaller inequalities which constitute 
in our theories. In my own lectures I no longer divide moun- 
tains into two kinds, mountains of upheaval and mountains of 
erosion, but simply treat the whole subject of mountains under 
the two heads of mountain formation and mountain sculpture. 
All portions of continents, it is true, are sculptured in this way, 
but this is especially true of mountain chains, which are the 
great theaters of erosion as of igneous agencies. When I speak 
of mountain formation, therefore, I mean only the formation of 
the great bulge or convex plateau which constitutes the chain ; 
but when Mr. Hunt speaks of mountains as “fragments of de- 
nuded continents,” he refers, of course, not to the chain, but to 
the smaller inequalities, or the effects of sculpture. It is cer- 
tainly one of the great glories of American geology, to have 
clearly shown by the study of the Appalachian chain the im- 
mensity of this work of erosion; that not only the smaller 
ridges and ravines, but great cafions, wide valleys and as 
peaks owe their origin to this cause alone. To Lesley, Hall 
and Hunt is chiefly due the credit of expounding these views. 
I confess their writings have been of immense service to me in 
my mountain studies. But I insist that a theory of these is not 
a theory of mountain chains. The older geologists, it is true, 
neglected far too much the effects of erosion, and attribu 
every peak, and ridge, and valley, to upheaval, or fracture, or 
engulfment; but there still remains the great bulge or convex 
plateau, the real chain, to be accounted for; for no one imagines 
this to be the result of erosion. 
Now it is precisely this convex plateau which, I had sup- 
posed, Hall and Hunt attributed to sedimentation. [had sup 
that they regarded the Appalachian chain as first a great convex 
