Tlic Peneplain. — Tarr. 363 
So-called monadnocks appeal to me as proof against the 
peneplain theory. Grant for the moment the destruction of a 
mountainous surface to the condition of a plain under subaerial 
denudation, and this reduction must certainly call for a very 
great lapse of time. Duriji^such reduction it may be ad- 
mitted that the soft rock will be much more reduced than the 
harder ones, and that the latter may stand well above the 
general level as residuals; but are the monadnock rocks essen-\ 
tially harder than the other hilltop rocks of the neighborhood?/ 
I know of no evidence that' has been made pub|ic that Mts.W 
Monadnock and Washington are made of harder rock than^ 
many of the much lower hillswithin a raidius df twenty miles 
from them. I know of no proof that they are more resistant 
than the Blue hills near Boston, nor that these are harder than 
the lower granite hills of Essex county, Massachusetts, a few 
miles awa}'. Is the rock of Mt. Washington more durable 
than that of Essex county, Massachusetts, or the rock of Mt. 
Katahdin or Blue hill, in Maine, harder than that of scores 
of lower hills not far away? I believe that I am correct in 
saying that there are no very distinct differences between the 
rocks of the monadnocks and the lower hills, in point of dura-: 
bility. while there is a difiference in elevation of more than a 
mile, and, even in short distances, of 2,000 or 3,000 feet. In 
some of these cases it is certain that the rocks of low and high 
hills are not markedly different. 
Without the existence of very notable differences in power 
of resistance, is it probable that a hill would stand several 
thousand feet above a plain which stretched all around its base, 
and which has been reduced to this condition by the slow 
process of subaerial denudation? After the regign surround- 
ing the monadnock had been reduced to the condition of a low, 
undulating hilly country, all the time required to plane it down 
to the condition of a peneplain has not been able to reduce the 
elevation of the higher, and hence more rapidly destroyed part, 
to approximately the same level ! 
It must be confessed that this op])osing evidence is based 
purely upon my own ability to conceive of the processes in- 
volved. In so far as this power of conception is strong or 
weak, this part of the argument is good or bad. I would put 
it forward with more hesitation if there did not ap[)ear to l)e 
