30 TACONIC PHYSIOGRAPHY. 
for a large part of the tract this is not difficult. The order and esti-j 
mated thickness of the formations are here given : 
Typical rock section of the Taconic region. 
Feet. 
(5) Silurian grit 1.400 
(4) Ordovician schist, or slate and shale (including some quartzite, 
unaltered grit, and limestone) 2,000-3,500: 
(3) Ordovician and Cambrian limestones 1,000-2,000, 
(2) Cambrian quartzite and schist or slate 1,000-1,500 
4, 600-8, 400 
(I) Pre-Cambrian gneisses, etc., not estimated. 
As the limestone of the valleys underlies the schist, these valleys] 
must have been originally covered with schist, and therefore about 
a half mile of schist besides the amount of the eroded limestone 
ought to be conceived as restored to the valleys. In such localities 
as Stone Hill, Rattlesnake Hill, and Monument Mountain, in' Berk- 
shire County, where the Cambrian quartzite comes to the surface 
in anticlines, the entire limestone formation as well as the schist 
ought to be conceived as added — i. e., at least 3,000 and possibly 
5,000 feet, leaving out the Silurian grit, which probably did not 
here extend into the Taconic Range. The schist masses themselves,: 
whose forms now diverge so widely from their structure, ought to bej 
conceived as restored to their original height and breadth and their 
transverse hollows and amphitheaters as filled. The synclinal moun- 
tains must correspond to original valleys, and the anticlinal valleys] 
to original mountains. The resulting form would be ver}^ much like 
that represented by AVillis in his Mechanics of Appalachian Struc- 
ture, a reproduced in PI. V, 6 y , if one conceives the drawing reversed 
so as to bring the landward side on the right. 
The entire belt between the Green Mountain Range and the Hudson 
and Lake Champlain must have been buried in argillaceous sedi- 
ments, all folded and metamorphosed in degrees of intensity decreas-j 
ing from the Green Mountain axis westward ; but, for reasons not 
fully evident, there was more metamorphism within the area of 
the Rensselaer Plateau than its distance from the Green Mountain 
Range would lead one to suppose. There may have been some irreg- 
ularity in the original sea" floor here.'' 
The Taconic folio (in preparation) affords evidence that east of 
Bennington the Cambrian quartzite extended to the center of the 
town of Woodford, almost to the 2,800-foot level, and also south of it 
in Stamford, and may have been continuous with that in the valley 
of the North Branch of the Hoosic, and Pumpelly and Wolff c evi- 
dently regard it as having probably covered the gneiss of Hoosac 
° Thirteenth Ann. Rept. T T . S. Geol. Survey, pi. 47. 
6 See Bull. U. S. Geol. Survey No. 242. 1904, pp. 48, 54. 
c Mon. U. S. Geol. Survey, vol. 23, 1894, pi. 3, Sec. B. and pi. G. 
