222 Tlie Aniericati Geologist. April, i89i* 
.Vlthougli agreeing in the belief that the theory of pene- 
plains involves a certain difference between the past and the 
present, we do not agree as to the bearing of this belief on the 
theory. Professor Tarr implies that the past, "whose history 
has been worked out by purely stratigraphic methods," is 
proved to be so like the present that the theory of peneplains 
must be wrong because it involves a past that is in some ways 
unlike the present. My opinion is that stratigraphic methods 
do not always disclose a past closely like the present (see B4) ; 
and that, even at their best, stratigraphic methods are not so 
complete in their revelations but that all other lines of evidence 
concerning the nature of the past should have a careful hear- 
ing. 
There are certain parts of the world in which frequent dis- 
orderly movements of the earth's crust appear to have con- 
tinued during several geological periods, including the pres- 
ent; for example, the Alps. The teachings of Mesozoic and 
Cenozoic stratigraphy in such a region would lend no support 
to the theory of peneplanation ; as little support would be 
gained from the teachings of denudation in the Alps. Indeed. 
I have been interested to learn that certain careful students of 
geomorphy in the neighborhood of the Alps have recognized 
that they were prejudiced against the theory because their ex- 
perience was gained chiefly in an uneasy part of the world. 
But there are other parts of the world which have been rel- 
ativeh' Cjuiescent for long geological periods: for example, the 
upper Mississippi basin, where all represented formations from 
the Cambrian down, are essentially horizontal and of moder- 
ate thickness. Stratigraphy, as there taught, would not be 
inconsistent with peneplanation: neither would geomorpli\ . 
and to illustrate this I have a little story to tell. During an ex- 
cursion with a friend native to. that part of the country. 1 
pointed out the very even skyline of a dissected upland, as an 
example of a peneplain. My friend dissented, thinking no 
such special explanation necessary; ordinary denudation 
would suffice, he thought, to produce the observed forms, with- 
out specification of control b} different baselevels. A year 
later, on meeting the same friend, our talk happened to turn 
on peneplains, and he said: 'T should like to show you an ex- 
cellent example of that sort of thing," proceeding to describe 
