GLACIAL PHENOMENA IN THE ADIRONDACKS 409 
produced. In the north Dr. Cushing has found indications of 
two peneplains and two periods of uplift... The upper level is 
marked by the somewhat uneven sky line of the hilltops ; the 
second by the valley levels. The diversity of altitude indicates 
that when the earlier erosion period was terminated by uplift, 
the surface was uneven. The observations of the writer in the 
south are in complete agreement with those of Dr. Cushing in 
the north. 
The uplift which terminated both the cycles was of a dome- 
shaped nature, being greatest in the Macy region. The result is 
that as the central region is approached the valleys grow deeper, 
the vertical distance between the two levels necessarily growing 
greater the more nearly the center of uplift is approached. The 
highest mountains stood out as low monadnocks above both 
peneplains. 
The dates of these two erosion cycles are a matter of much 
uncertainty. The uplifts which terminated them are certainly 
of comparatively recent date, since, as observed by Cushing, the 
axis of elevation is most pronounced, and the fault scarps of the 
same age are remarkably fresh. Definite correlations cannot be 
made until the topographic maps are completed, not only for the 
Adirondack region itself, but for the region connecting the 
Adirondack with the Appalachian region. There seems a strong 
probability that the upper Adirondack level will prove to be the 
northward extension of the Cretaceous peneplain of New Jersey 
and Pennsylvania.? Brigham has suggested? that the plateau 
south of the Mohawk is to be regarded as a possible northward 
extension of this Cretaceous plain. This plateau, like the Kit- 
tatinny peneplain, is almost level, and is cut on soft Palaeozoic 
rocks. As already shown, there is reason to believe that the 
™ Geology of Franklin County,” Zighteenth Ann. Rept. N. Y. State Geologist, 
1898. 
2W.M._ Davis, “ The Geological Dates of Origin of Certain Topographic Forms 
on the Atlantic Slope of the United States,” Bul. Geol. Soc. Amer., Vol. II, p. 560. 
3A. P. BRIGHAM, “ Topography and Glacial Deposits of the Mohawk Valley,” 
Bull. Geol. Soc. Amer., Vol. 1V, pp. 183-210. 
