58 C. H. HITCHCOCK 
mentation. The first sediments must have been accompanied by 
a greater flow of eruptives than those formed later. (5) Much 
of the hornblende-schist is igneous, related in origin to lacco- 
lites. (6) Serpentine and steatite are alterations of material orig- 
inally igneous. 
Applying such principles to the classification of the. rocks of 
northern New England, we may improve on the report in sev- 
eral particulars. (1) Archean rocks are not eliminated from our 
list. They exist as oval areas, such as have been indicated, in 
the Stamford gneiss and south of Mt. Killington, Vermont, in 
the Hinsdale, Massachusetts, area, the Hoosac Mountain, and 
elsewhere. I recognize the porphyritic gneiss in the Stamford 
rock and in the Hoosac tunnel as Archean. (2) Our hesi- 
tancy about the place of the Bethlehem gneiss is met by recent 
observations. They are batholites, containing inclusions of the 
adjacent mica schists. It does:not follow that all these proto- 
gene areas are of the same character; each one must be studied 
by itself. Some may be altered gneisses, and others sandstones 
where feldspar grains prevail. (3) Later observers are not agreed 
as to the nature of the upper part of the Green Mountain 
gneisses. What is apparently the same material is called ‘‘ Cam- 
brian gneiss’? on Hoosac Mountain by Professor R. Pumpelly* 
and ‘“‘Algonkian” by Mr. C. L. Whittle? near Rutland, Vermont, 
Professor Emerson in adopting Pumpelly’s view finds a series of 
anticlinals of the same material further east, which probably 
correspond to the similar folds referred above to the lake 
gneisses. (4) Later conclusions respecting the age of the rocks 
entering Vermont and New Hampshire are entertained by the 
Canadian Geological Survey. There are three areas of pre-Cam- 
brian, viz., the axis of the Green Mountains; the Sherbrooke 
belt, reaching Lake Memphremagog, and along the international 
Huronian. Better amend the latter so as to exclude the Cambrian, rather than cumber 
literature with a term harder to write, less euphonious, and with practically no differ- 
ence of signification. 
Monograph XXIII., U.S. Geol. Survey. 
2? This JOURNAL, Vol. II., p. 396. 
3 Bull. Geol. Soc. Amer., Vol. L., p. 453. 
