LEAD BEARING BOCKS OF THE UNITED STATES. 
175 
In the north-western part of New York, the sulphuret of 
copper is found connected with the pyrocrystalline limestone, 
in strings and bunches. Its origin in this instance may also be 
attributed to a like cause. 
THE LEAD BEARING ROCKS OF THE UNITED STATES. 
§ 106. The only ore of lead which is found in sufficient 
quantities to pay a profit to the miner, is the sulphuret of lead 
or galena. It is found in rocks of several epochs. The Pyro¬ 
crystalline, the Taconic, Silurian and carboniferous, are each of 
them lead bearing. In the Alleghanies and other primary 
ranges, it is found in veins. The gneiss of this great range is 
generally the repository of it, as at Rossie, St. Lawrence county. 
It occurs in veins also in all the systems I have named. At 
Ancram in Dutchess county, it is in the Taconic system; near 
Spraker’s, on the Mohawk, and at Martinsburgh, it is in the 
Lower Silurian. At Wisconsin and Iowa, Upper Silurian. In 
Derbyshire, England, it is in the Carboniferous system. 
The Rossie lead mine has been worked to a greater depth 
than any other lead mine in the country, and hence may be 
referred to for the purpose of illustrating the general facts 
which pertain to the repositories of lead in gneiss, as well as 
the other rocks which belong to the same class. I have already 
had occasion to refer to the lead vein of Rossie, the structure 
of which is exhibited in the figure. The vein is exposed at 
this place in consequence of a shift in the gneiss by which it 
has been elevated thirty-five or forty feet above a low swampy 
country, which bounds the outcrop of the rock on its eastern 
side. The peculiarities and characteristics of this vein as well 
as other veins, are exhibited in the cut, Figure 25. 
The middle dark broad line represents the position of the 
galena, imbedded in a calc spar on each side, and which fills 
the fissure. When the outcrop of the vein was exposed, the 
white gangue of spar, and the brilliant seam of lead in the 
