Granitic veins and beds in Chester, Mass. 251 
‘supported on the vertical edges of the strata of mica-slate. 
An area of several square rods is exposed to examination, 
anconcealed by the soil. It is uniformly about four inches 
thick and fills the inequalities of the inferior rock. The 
Yein is not in one continued plane, but projects downwards 
into the mica-slate, and gives off narrower branches which 
terminate within a few feet of the principal vein. This 
vein appears three times in an area of twenty square rods, 
though not inan unbroken mass, yet they were evidently 
once connected. 
Another position in which granite occurs may be seen 
fig. 2. These veins and bed were discovered in Norwich. 
allel veins eight inches thick come up from below and 
unite with the bed. The bed is irregular in its shape, 
and gradually tapers each way, till it terminates in points. 
‘ At these points, it is distinctly seen to rest on the edges 
of the strata and not to penet urate between them ; it once 
extended farther N. and S. at present, for masses of 
granite are still seen ampere he mica-slate for several 
tods, On the east side, the rock which Constitie the 
‘walls j is entirely broken away, and exposes the w 
‘to view. There are many other masses or beds or granite 
which are apparently in the situation of this last, though 
it cannot be determined whether they are connected with 
veins, yet it is probable they are. It is very certain that 
in many places the principal masses of granite do no 
tee deep, as they can be seen to become thinner as 
they Seseand between "hie eptrata of mita-slate, and a few 
which I have seen, actually terminate after 
“Penetrating a few inches downwards. | 
ig. 3. PI. JI. represents a section of a granitic bed*. It 
‘against th -slate on the west, but on the east 
i It is four feet thick, and i is twisted 
and. prismatic mica. One crystal of blue tourmaline is to 
Neen thége, inghes J in diameter. One ofgreen has been 
*Lam ee wi vith he common definition of pee and veins. | 
should e: sy all the granite which occurs here, granitic some In- 
stances it js impossible to determine whether the ata isin bed or veins. 
