162 
AM ERIC AN GEOLOGY. 
no diminution of gold in the deeper parts of the vein. Like 
other veins of metal, it is variable in quantity—rich and lean 
places are met with in the same mine; but the Gold Hill mine, 
the McCulloch mine, Conrad Hill, and all ihose which have 
been skillfully worked, yield as much gold now in the aggre¬ 
gate as when they were first opened. It must, however, be 
acknowledged that though the quantity of gold obtained below 
water may equal that above, yet the increased expense of min¬ 
ing may consume all the profits of the business, and, in many 
cases, prudence would suggest the abandonment of deep mines. 
DIRECTION OF THE AURIFEROUS VEINS. 
§ 97. The extremes in the direction of veins lie between 
N. 10° "W., and N. 70° E. The ordinary limits lie between N. 
20° E. and 70° E. Their direction of dip is northwest in 
North Carolina, and the angle of dip varies from vertical to 
20° at the surface, while where it is as small as 20°, the dip 
becomes greater in its progress downwards. The ordinary dip 
is such that a vein will make to the westward seven or eight 
feet in seventeen or eighteen feet perpendicular descent. 
OF THE AURIFEROUS VEINS WHICH PASS FROM ONE ROCK 
TO ANOTHER, AND WHOSE COMPOSITION AND AGE ARE 
DIFFERENT. 
§ 98. In North Carolina a belt of granite underlies parts of 
Guilford, Davidson, Cabarras, and Mecklenburg counties. The 
east side of this granitic belt is bordered by a fine greenish 
slate. It is the opinion of well informed miners and geologists 
that the auriferous lodes pass from the granite into .the slate. 
The observations have been made where the slate is thin, and 
overlaps the granite. Fears were entertained that certain 
lodes would become valueless for gold when they entered the 
granite, agreeably to a law which is well established in other 
mining districts. My opportunities for observation are too 
limited to warrant the expression of an opinion; but I have 
