224 The American Geologist. April, i899 
It seems to me a prejudgment of the case to enter it with the 
conclusion that the lands do not stand still long enough for 
peneplanation. Certainly they do not stand still long enough 
in certain regions; witness the manifest effects of uneasiness 
in the varied and unconformable stratified deposits, or in the 
repeated renewals of dissection in the Alps. But the opposite 
conclusion is enforced by both lines of evidence in the Pied- 
mont region of Virginia. 
Another example may be taken from the West. The up- 
land of the plateaus trenched by the Colorado canyon is l)y no 
means a level surface; but if the fault cliffs and the monoclinal 
slopes by which it is dislocated, the canyons by which it is dis- 
sected, and the volcanic cones by which it is embossed were 
subtracted, the remaining relief could not, if one may judge 
by Button's vivid descriptions, be so great but what the sur- 
face might be called a peneplain, especially if due regard is 
had to the vast volume of material removed in its preparation, 
as attested by the huge clififs of recession on the north. It is 
true that a certain part of the upland seems to be a structural 
plain ; that is, its surface agrees rather closely with that of 
the more resistant Carboniferous layers; but when looked 
at broadly, the upland is seen to bevel gently across the edges 
of the layers, which dip northward at a faint angle. In ex- 
planation of this great denuded upland. Button says that the 
evidence points decisively to a "period of quiescence" in Ter- 
tiary time; "while it prevailed, the great Carboniferous plat- 
form was denuded of most of its inequalities, and was planed 
down to a very flat expanse" (Monogr. II, U. S. G. S., p. y/^. 
The supposition of a period of active uplift, during which 
the incision of valleys was begun, and a period of quiescence, 
during which the hills were worn away, "would give just such 
a country as we see at present" (Ibid., 225). Inasmuch as the 
platform is now in process of active destruction by the widen- 
ing of the main and branch canyons, a strong uplift must be 
postulated after the period of quiescence during which the plat- 
form was denuded. In all this inquiry, the argument based on 
processes of denudation is fully as logical and as legitimate as 
the argument elsewhere based on the processes of deposition. 
But it has never been my intention to imply an absolute 
still-stand of the earth's crust durinc: an entire cvcle of denuda- 
