234 The American Geologist. April, i899 
SV C I. The alternative theory aims chiefly to explaiii the ex- 
isting forms of Nezv England rather than those of better fin- 
ished and better preserz'cd peneplains. It is a matter of regret 
that a theory intended to replace the theory of peneplanation 
should have been tested by its author chietly in New Eng- 
land, whose highest and most rugged ])arts are generally ta- 
ken as examples of grouped monadnocks. I should not be at 
all disposed to say that the "pene])lains of New England and 
New Jersey * * * have been most fully studied, and rest 
upon the firmest basis" (p. 353). Southern New England 
would have been a fairly satisfactory area, but when the White 
and Green mountains and the mountains of Maine are in- 
cluded, the example to be explained falls largely outside of 
the scope of peneplanation. The reference to Labrador (p. 
366), as an area unfavorable to the peneplanation of New Eng- 
land, seems altogether a::ide from the case. However, if the 
alternative theory of mature dissection is really capal)le of 
supplementing the theory of peneplanation, it should snfTice 
to explain not only rugged New England, but also the many 
better finished and better preserved peneplains in other parts 
of the world, some of which have been referred to above. 
\j\ (1 2. The subeqiiality of mountaifi higJits. The develop- 
ment of a rough equalitv in tlie hight of mountain peaks bv 
the faster destruction of the higher summits, on account of the 
greater violence of weather changes and of the absence of 
tree and soil covering at great bights, has been announced by 
Penck (Morphologic der Erdoberflache) and by Dawson (Ge- 
ology of the Kamloops area, Geol. Surv. Canada, 1894) and is 
now independently suggested by Professor Tarr. ABC and 
ADE, fig. 2, are in this way changed to FGH and FJK. The 
processes appealed to are not identical in the explanations of 
the three authors, but not having the writings of the two form- 
er at hand, I cannot give details. The approach to ec(ual bight 
o\ many peaks of different structure in a given mountain 
group may be thus explained, as in the Alps, or in the Rocky 
mountains of Colorado: if any one felt per contra convinced 
that this subec|uality might be the result of the deep dis- 
section of a greatly elevated peneplain, the discussion would 
doubtless be interesting. 
The subequality of mountain bights being once gained, all 
