Tlic Peneplain. — Davis. 227 
"I should think that drumlin ought to be more eroded if it 
has stood there unprotected since the ice sheet disappeared."" 
Evidently such an opinion is based on a preconception of too 
long a post-glacial interval ; for how can the interval be meas- 
ured except by what has happened to the drumlin during its 
passage! How can past time be estimated except by studying 
what has happened during the progress of its ages! 
B 3, No part of the earth reveals cve}i an approximation 
to a peneplain. It is contended that as all the reputed pene- 
plains now known are of the past, and that as all are now more 
or less fragmentary, "no part of the earth reveals even an ap- 
proximation to this supposed condition" (p. 355). This seems 
to me an over strong statement in view of the form of such dis- 
tricts as the Piedmont belt, above referred to; but leaving 
aside even the best examples of well-finished and slightly dis- 
sected peneplains, let us consider some examples of peneplains 
that were submerged and. vmconformably buried after their 
surface had been reduced to faint relief, and that are now mere 
or less visible where valleys are cut into the compound mass 
in consequence of uplift. It is true that these peneplains are 
not today standing in the position in which they were formed, 
that they make a very small part of the earth's actual surface, 
and that they are imperfectly open to observation; but it 
seems to me that they give strong evidence of the verity of 
peneplains, and that they certainly suffice to set against the 
strong assertion quoted at the opening of this paragraph. 
An excellent example of a plain of denudation is exposed 
in section on the walls of the Colorado canyon. It is well 
shown — to those who cannot see the canyon itself — in several 
photographs by Jackson; it is "the record of a long time when 
the region was dry land," as already quoted from Powell ; and 
it is thus described by Button ; "The base of the Carboniferous 
has a contact with unconformable rocks beneath, which was 
but slightly roughened by hills and ridges. In the Kaibal> 
division of the Grand canyon .... we may observe 
. . . a few bosses of Silurian strata rising higher than the 
hard quartzitic sandstone which forms the base of the Carboni- 
ferous. These are Paleozoic hills, which were buried by the 
growing mass of sediment. P)Ut they are of insignificant mass, 
rarely exceeding two or three hundred feet in height" (U.S. G. 
