Tlic Peneplain. — Tarr. 359 . 
nocks. Then, drawing '. section on scale, I have computed- 
the area occupied by the crests, reaching an elevation within 
300 feet of one another and compared this area, which is all 
that is now left of the "peneplain," with that above or below 
the level. In each case the area occupied by the crests of thisj 
elevation is less than 25 per cent of the entire area examined, 
and is generally about 10 per cent. Assuming this to be the 
remnant of the ancient peneplain, as has been done by the 
advocates of the theory, and reconstructing this supposed an- 
cient plain, by filling in the valleys and raising the lower hills, we 
have a peneplain constructed of which 75 to 93 per cent has , 
been gratuitously supplied because of the moderate uniform-, 
ity of crests whose total area is from 10 to 25 per cent of the 
whole. Moreover, this uniformity of crests has been obtained 
only after making use of two assumptions, and by means of 
them somewhat arbitrarily, disregarding those irregularities 
which are explained as monadnocks and the result of tilting. 
As the result of these considerations. I cannot but believe 
that the basis upon which the peneplain theory is supported 
is not altogether solid. In point of fact there seems to be very 
little real evidence upon which to construct the ancient pene- 
plain, an.d I am led to raise the query whether, even granting 
in its entirety the evidence claimed, we would be warranted' 
in drawing so broad a conclusion from so small a basis of 
fact. 
The second fundamentally important point in the pene- 
plain explanation is the claim that we get this uniformitv 
notwithstanding the complexity of the rock "structure." That 
is to say, I suppose, there is a lack of sympathy between the 
level-topped hills and the rock texture and position,''' excepting 
possibly where the residual monadnock rises above the ancient 
plain. That the stratigraphy of the region here considered 
is complex, and the rocks variable in texture and attitude, is 
■ evident, but I (luestion whether there is after all such a lackv 
of sympathy between topography and rock structure as would' 
*From Prof. Davis' paper it is evident tliat attitude of the rocks/, 
is considered as the main element under "structure," nnd I am not 
quite certain whether he meant to include texture under the tenn. 
as is so commonly done. Whether he did or not, the consideration 
of this point is warranted, since some have certainly considered 
structure as synonymous with both te.xture and attitude. 
