106 Geology of Deerfield, §c. 
alternating with mica slate, siliceous slate, or chlorite slate. 
Tt is thus coloured to show the extent of the argillite, and not 
from a belief that this rock is of the transition class; for in 
this region the argillite is undoubtedly primitive. Some quar-— 
ries of this rock have been opened in Massachusetts; and in 
Vermont are extensively wrought. I have not learnt how fat 
the argillite extends northward in Vermont and New-Hamp- 
shire. Its strata are almost perpendicular, inclining a few de- 
grees to the west. 
The primitive region on the west side of Connecticut rivet, 
included by the map, is made up of mica slate, as a prevailing 
rock, particularly in the northern part. Hornblende slate 
sometimes alternates with this, and sienite appears in varios 
places, though its strata are generally thin. Limestone also 
occurs in Deerfield, Conway, Colrain, &c. of a dull brown 
colour. It contains so large a proportion of silex that it is often 
but little removed from granular quartz. Lime for building 
has sometimes been obtained from it. A range of granite, col 
taining veins of lead ore, appears at Southampton, and pre 
ceeds to Hatfield. ‘North of this, the other rocks cover it ant 
it does not again rise within the limits of the map. 
Sienite is the prevailing rock on the east side of Connecticut 
river, in the primitive region, more particularly in the southe™ 
part. In some places a narrow stratum of mica slate lies nest 
to the conglomerate of the secondary formation, and 4 lon 
range of graphic and common granite has been observed 
Amherst and Leverett, lying next to the mica slate. ‘Other 
veins of granite also traverse the sienite ; and gneiss occurs # 
many places. The proportion of hornblende in the sienite ® 
generally small, and mica is often present in considerable p™ 
portion. Porphyritic sienite is common in this quarter, a! 
steatite occurs in its eastern part. 
Most of the primitive region on the map is broken at 
mountainous, being made up of parallel ridges and detache! 
eminences. The strata run nearly north and south, and <p 
to the east at angles between 20° and 60°. It would be eas 
to extend the map on the west to the top of Hoosack mount!” 
since the country is all primitive; and on the east the pam 
