J. D. Dana—Helderberg rocks in the Connecticut Valley. 347 
contained intercalated portions of the same slate; further, the 
.. of slate in this ledge increased much to the eastward. 
art of it contained the mica crystals very thickly disseminated 
- so as to crowdedly spangle the surface of a cross-fracture—a 
variety closely like part of the rock at the railroad cut just south 
the South Vernon depot. Thus the fact that the Bernards- 
ton garnetiferous mica slate and the South Vernon hornblende 
rock were of one and the same formation was made certain, 
for here, besides occurring in alternating beds, they graduate 
into one another. The position and dip of these ledges indica- 
ted that they were all inferior in stratigraphical position to the 
quartzite of the hill above mentioned. 
_ Decending the quartzite hill on the north side and continu- 
ing in that direction, the rock changed first to the same mica 
slate, the slate outcropping at one place from beneath the quartz- 
e prisms of mica in some of the slate were an eighth 
ofan inch in breadth and length; and, on a worn surface of it, 
they appeared as dull black, squarish spots. The garnets in all 
Hast of this region (marked CC’ on the map) there are two 
EE’, one to two hundred feet high, separated 
Nets forind seattered Gver ihe slopes and summit of ridge DD’, 
oO other outcrop was met with. on 
n the meadow at the eastern foot of ridge DD’, lies the 
slate of Purple’s quarry, having the dip and strike already 
8 ; and it is beyond question the Bernardston slate. what- 
ever be true of the gneiss of ridge : i 
ty the top of the ridee (EE ds bounding this valley on the 
east, near E’ and BE", there is true quartzite, having a dip of 20 
