STAUROLITE CRYSTALS AND GREEN MOUNTAIN GNEISSES. 659 
The fossils found in Vermont lead to the conclusion that the 
limestone represents the Trenton era as well as the Chazy. The 
overlying mica schist and other associated rocks have a thickness 
of at least three thousand feet; and, if the limestone is Trenton 
in part, they belong to an era later: either to a closing part of 
the Trenton period, or to the period ot the Hudson River or 
Cincinnati group. 
In any case there is no reason to doubt that the staurolites 
occur in rocks of the later part of the Lower Silurian age, and 
strong reason for the conclusion that these schists are in age veri- 
table Hudson River rocks. 
On this view, the Hudson River or Cincinnati group, in the 
Green Mountains — alike in Connecticut, Massachusetts and 
gists), well-characterized gneiss of various kinds, some of it much 
contorted, and granitoid gneiss. 
At a locality at South Canaan ines in Cobble Hill, the lowest 
rock over the limestone is quartzite; next follows mica schist 
passing into gneiss; and above this there is a light-colored grani- 
toid gneiss, breaking into huge blocks with very little of a schist- 
ose structure. 
Near the boundary of the towns of Tyringham and Great Bar- 
rington, four miles east of the latter village, a locality long since 
studied by Mr. R. P. Stevens of New York, and by him pointed 
out to me, there are, over the limestone, alternating beds of 
quartzite gneiss and limestone dipping at a small angle to the 
eastward. Commencing below, the succession is 
1. Granular limestone, that of the valley. 
anular limestone, 40 feet. 
8. Mica schist, 6 to 8 feet. 
9. a partly Tamis e = feet, forming a high bluff,— the site of Devany’s 
a Gneiss, forming the ‘top of vay blut, and aan cca thickness ina age te to the 
northeast, b 
oe a 
ps 
2 
= 
2 
The fact that quartzite, limestone abd gneiss or mica eR 
here alternate with one another is beyond question; and, if I 
am right in the age of the deposits above suggested, the alter- 
