Perry.] 146 [February 28; 
pret the features of all, or even of any other localities, by what he 
may happen to know of some limited vale. Indeed, many peculiari- 
ties of each well-trodden district can be in most instances better ex- 
plained in the light which comes from the careful investigation of 
more perfect examples furnished by some other neighborhood, or of 
various classic fields combined. This must be clear, since no single 
area can be ordinarily expected to supply type-characteristies of all 
that we may wish to study within its bounds, or even of the manifold 
peculiarities which it is desirable to investigate, in any given line of 
research. These thoughts are suggested by what appears to be a 
fact in regard to some of: the generalizations in the paper under re- 
view. The question naturally arises whether the author has not in- 
terpreted the glacial features of his own vicinity mainly according to 
what he has found in ‘“ the books ;” whether, again, he does not to a 
considerable extent describe the country at large in the light in 
which he thus sees “the New Haven region”; and whether he 
might not understand even New Haven and its environs very differ- 
ently, if he were carefully to study many other portions of New 
England, in which some features of the Post-Tertiary times have a 
better exhibition than in any seashore neighborhood ; while they are 
comparatively free from certain obscurities and perplexities, which 
the vicinity of the ocean makes doubly uncertain. . 
Again, Prof. Dana’s views of the Post-Tertiary era in New Eng- 
land seem to be in many points erroneous, and thus misleading. On 
such a subject as Geology no one, it is true, can know everything 
from personal observation. ‘This needs ever to be borne in mind ; 
at the same time what is not understood with certainty ought not to 
be published as trustworthy. Now the question may be raised 
whether the writer of the pamphlet under consideration has not 
erred in the direction suggested; whether much that he has ex- 
pounded be not at least questionable; whether many of his positions 
be not clearly erroneous. Let me cite an instance. In teaching that 
olaciers, breaking, take up into themselves, and become engorged 
with, the detrital matter that is abraded from the underlying rocks, 
does he not misapprehend the nature of such ice-masses? and does 
not this single misconception lead to others, such as, (to mention one 
only,) that drift is not deposited until the glacial mass in melting dis- 
gorges the detrital matter it had before engorged? But enough; 
this example must plainly show that some of the Professor’s state- 
ments are erroneous, and that some embody but partially the whole - 
truth. He theorizes with all boldness, and he utters his theories of- 
