TJic Peneplain. — Davis. 237 
The ancient mountain structures show no sign of weakening 
as they approach the shoreHne, and we may fairly suppose 
that there has been about as much denudation to be done there 
as further north. From southern New Hampshire, across 
central Massachusetts and Connecticut, there is no indication 
of a weakening of the rocks; a good variety of more or less 
resistant gneisses and schists occur all across this district." 
Difference of climate cannot be appealed to as a cause of faster 
denudation and beveling near the coast, for the climate is 
more severe in the interior. The streams are larger and the 
valleys are necessarily lower and broader near the coast than 
in the interior, but the interstream uplaiids are under essen- 
tially similar conditions in the two regions. A rough equality 
of mountain bights being established, as H, A, B, fig. 4, there 
is then no reason for the greater action of the weather on a 
square foot of surface at B than at A. The master streams 
having gained a graded slope, GEF, there is no reason for 
the denudation of A to hesitate at the hight C, a thousand 
feet above the streams, while B is reduced to D, only a hundred 
feet or less above the streams. Hence I have to conclude that 
whatever strength there may be in the propositions quoted at 
the opening of this section, they are not presented in a way 
to make it apparent. The tilting of a previously denuded sur- 
face seems a relatively simple and safe way of accounting for 
the relation of the upland and stream profiles, CD and EF, 
as has been suggested above (A6) ;but tilting has noannounced 
place in Professor Tarr's theory. The omission of so com- 
monplace a movement is the more curious, inasmuch as fre- 
quent movement of some sort must be characteristic of a the- 
ory that "requires no long periods of relative quiet" (p. 369). 
C 5. Nezv England and Nciv Jersey eis maturely disecfed^ 
mountains, rejuvenated. It is maintained that the regions 
especially under discussion have been "lowered to the stage 
of full maturity, then elevated and made more rugged." and 
that although the surface has always been mountainous, it was 
"once less mountainous than now, because of the recent up- 
lift" (p. 365). There are various other parts of the world to 
which a similar description might be applied: the indication of 
full maturity being found in the well-opened valleys of the 
larger streams, ABC, fig. 5, developed with respect to a 
