Trans. N. Y. Ac. Scé. . 28 Nov. 14, 
The stream in the valley referred to finds its way to the sea through 
a narrow pass, which, as attested by the rapid wearing of the coast lire 
and its present configuration, Could only have been of (geologically 
speaking) very recent origin. How the valley could have been drained 
prior to the existence of this outlet was a question which might be met 
by various hypotheses ; and one of these was that there might have 
been a slight unequal local change of level, sufficient to have had the 
effect of tilting the surface of the valley, so that its waters were shed 
then in a direction opposite to that which they now take. This was 
nothing more than the veriest hypothesis, made many years ago, with- 
out any subsequent attempt at verification. It may suggest, however, 
the possibility of such slight local changes occurring, in addition to the 
greater movements already distinctly recognized, and the desirability of 
careful investigation to discover whether such may not be traced in the 
altered direction of streams and in the existence of ancient and unused 
water courses—even in our own neighborhoods. It may be added 
that such local tiltings of parts of the earth’s crust would necessarily 
influence the course of subterranean as well as of subaerial waters, thus 
altering the distribution and force of springs at the surface. 
Dr. J. S. NEWBERRY stated that the Catskills presented a more com- 
plex bit of topography and geology, and one that had been more dis- 
cussed than perhaps any other of similar area in the country. It was 
once supposed that these mountains were composed of a single geolog- 
ical formation, which, from this fact, was called the Catskill group ; 
and it was suppcsed to be a detached table land, deeply carved by 
erosion. The late Col. Jewett, of Albany, found strata containing 
Chemung fossils in the Ca'skills, and from this inferred that the moun- 
tains were composed of Chemung strata. Prof. Hall and Prof. Guyot, 
with their assistants, then made a careful study, running through 
several years, of the topography and geology of all the surrounding 
region. Their labors established the fact that the Catskills are not an 
isolated mountain group, but belong to the Alleghany system and are 
formed by a series of folds or arches composed of the Chemung and 
Catskill rocks. Of these folds, the convex arches, as is usually the case, 
were cracked and broken and, therefore, yielded readily to erosior, 
while the concave arches, protected and solid, yielded less readily and, 
in time, by the wearing away of their surroundings, were left in relief, 
forming ridges with a synclinal structure. Hence it will be seen thet 
the topography of the Catskill region is chiefly the resu!t of erosion. 
So far as regards the changes of level from subterranean causes, re- 
ferred to by Mr. Julien, it would certainly be strange if the foundations 
of the Catskills were proved to be stable. The old name, “¢erra 
Jjirma,” once applied to the crust of the earth, is a complete misnomer, 
