J. D. Whitney on changes in Mineral Veins. 57 
setts; and the St. Lawrence County mines in New York. In 
none of these has any marked change taken place near the sur- 
face. In one part of the Southampton (Mass.) lode a few oxydised . 
ores were found when the mine was first opened, but they were 
but small in quantity compared with the mass of the unaltered y 
ore, This state of things is a great drawback on the opening 
of the New England mines since the expense of a 
driving in the hard granite and quartzose rocks is enormous. In 
North Carolina, South Carolina and Georgia, on the oe hand, 
the gneiss and slates are often found over a great extent of terri- 
tory completely decomposed and softened, so ate may be 
excavated with the pick and shovel, down to a depth of fifty or 
a hundred feet. I have known a shaft sunk in North Carolina in 
the rock to the depth of sixty feet in one week. 
Iu the veins of that State, the principal, indeed, almost the only, 
one near the surface is an auriferous gossan resulting from the de- 
Composition of iron pyrites, with which a little copper pyrites oc- 
Of this latter ore, the quality in several instan- 
crease with the depth of the workings. If the 
flon of the most importance is: what kind of ore and how much 
of it is likely to be found in sinking into the undecomposed veins 
beneath the level of the black ore. This, we believe, cav only be de- 
termined by actual trial. If in cleaving out the deposit of ore, which 
lies upon the hard veinstone beneath, there should be bunches of 
selves, why considerable quantities of the yellow ore of copper 
should not be found within areasonable depth. Still it is not im- 
1é fissure veins they may be found to have been richest hear 
the surface and not me siyabte of being worked with profit in 
hard rock, | 
. — Suntzs, Vol. XX, No, 58.—July, 1855. 8 
