Orographic Conclusions. 261 
constituent) ; the absence of chrysolite rocks, corundum-bear- 
g rocks, and zircon-bearing rocks. Moreover, coarse flesh- 
colored granites and coarsely porphyritic gneiss or granite are 
ed 
not among the rocks mentioned. 
The frequent abrupt transitions between quartzyte and 
gneiss is of so much interest that I may refer to it here again, 
and repeat that it means abrupt transitions from sand deposits 
to mud deposits in the old seas, just as are now common along 
the borders of the modern. 
In the condition of sedimentary rocks, the differences which, 
under metamorphism, have led to so long a list of rocks would 
hardly be apparent to the eye, and generally be overlooked in 
a description—a little difference in color, or in texture, or in 
proportion of sand, or in compactness, or thickness of bedding, 
being the chief points visible in an unaliered rock made of clay, 
mud or san 
3. OROGRAPHIC CONCLUSIONS. 
Among the orographic relations between the limestone 
region in Vermont and Berkshire I mention here only two. 
(l.) The first relates to the positions of the rocks, and the 
connection between position and height. 
_ a. Along the Central slate-belt of Vermont and its continua- 
tion in Berkshire, called the Taconic range, the slates, for the 
most part, have a high eastward dip; and the facts show that 
where this is the case they are pushed over in synclinal folds 
(sometimes with subordinate or local anticlinals and synclinals), 
the axial plane of which dips eastward. 
_ 6. At intervals the slate-belt rises into peaks over 2,500 feet 
in height. Such peaks occur wherever the synclinal is a broad and 
comparatively shallow one. ‘ 
In Vermont, this is the case in Dany Mountain, Mount 
Dorset or Eolus, Spruce Peak, Equinox Mountain and Mount 
Anthony, as illustrated on pages 346, 347, of the last volume 
of this Journal. The explanation is simply—that a very br 
synclinal or trough holds a very large mass of mountain mate- 
; and that, on account of its magnitude, and often also its 
