224 Connecticut River Valley. 
cover the upper sandstone layers of the Deerfield and Sunderland 
mountains, would, in the present state of the valley, extend to, and high 
up the Fifteen mile falls. Its waters would penetrate far into the 
valleys of the larger tributaries of the Connecticut, and the superfi- 
cial extent of its surface would be about four times as great as the 
superficial extent of the secondary formation. Considering how the 
materials of this formation have been collected from all parts of 
the Connecticut river valley, it is inconceivable that no sandstone 
should have been formed in the upper half of the valley, none in the 
valleys of the tributaries, and none in the present course of Con- 
necticut river below Middletown, if the figure of the superficial rocks 
has not beeen changed, and the lake in fact was high enough to cover 
the Deerfield mountains, at their present elevation. 
Neither could layers have been formed by deposition or subsi- 
dence, in the almost perpendicular position in which some of them 
repose, in place. Sand or clay, whether above water or under water, 
falling upon a surface inclined seventy five or eighty degrees to the 
horizon, could not rest and cohere, preserving the perfect order and 
uniform arrangement which exist in the plates and layers of those al- 
most perpendicular strata. Rocky strata, so greatly inclined, must, 
therefore, have undergone a great change of position, subsequently 
to their formation. 
VII. Greenstone Formation. 
Extent.—F acts remain to be mentioned which will render it not 
merely probable, but almost certain, that changes have taken place in 
the position and elevation of the secondary strata. A variety of rock, 
different and distinct from both the primitive and the secondary, 
known under the names of trap, and greenstone, extends with occa- 
sional interruptions, from near the north line of Massachusetts to 
Long Island Sound. Beginning above Greenfield, it forms a hill 
several miles along the bank of Connecticut river. Again the green- 
stone rises, in the borders of Belchertown, and forms Mount Holyoke, 
one thousand feet high,* which running eight miles towards the west, 
disappears at Rock Ferry, below Northampton. On the opposite 
side of the Connecticut, the trap rock rises again, in Mount Tom, to 
the height of a thousand feet, and so continues about six miles to- 
wards the south, where it sinks to a hill. The same rocky range 
* One thousand feet above the river at this place, and one thousand and one hun- 
dred feet above the sea. 
