112 Professor Jameson on the Geognostical Relations 
mixture of the granite with the bounding strata, or their mere 
attachment without intermixture ; and often numerous veins of 
granite shoot from the imbedded mass into the adjacent rocks. 
c. The imbedded granite masses are sometimes completely 
enveloped in the surrounding strata, but more frequently a con- 
siderable portion of the mass rises high above the bounding 
strata. This is owing partly to the influence of the weather 
removing a part of the superimposed strata, and partly to the 
original formation of the mass itself. 
Granite in Beds. 
Granite frequently occurs in tabular masses or beds, which 
are parallel with the bounding strata. These vary in breadth 
from a few feet to several hundred feet ; and from a few yards 
to several hundred yards, in extent. These beds, at their line of 
junction with the neighbouring strata, are sometimes distinctly 
separated without any transition or intermixture ; while, in other 
instances, transitions are to be observed, and also intermixtures 
with the superimposed or subjacent strata. Veins or branches of 
the granite also occasionally shoot from the beds into the bound- 
ing strata. 
Granite in Veins* 
Veins of granite, as already described, shoot from imbedded 
granite, and also from granite beds into the adjacent strata; but 
besides these, numerous veins are met with, w^hich are isolated 
and unconnected with any bed or imbedded mass of granite. 
These veins vary in magnitude from half an inch to many 
fathoms in width, and from a few* inches to many fathoms in 
length. They are sometimes very tortuous in their course, and 
occasionally send out from both sides numerous smaller lateral 
branches or veins. In some of these veins there is no intermix- 
ture of the vein mass and the bounding rock ; in others there is 
an extensive intermingling of the two. 
Rocks in which Granite occurs. 
Not above forty years ago, it was a general opinion that granite 
occurred only under, and in contact with gneiss, and Avas there- 
fore entirely Avanting in all the other rock formations, This^ 
