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[Assembly 
have perforated the grit rock, and entered the subjacent slate rocks, in 
less than that distance. 
It is a fact well ascertained in mining, that metalliferous veins change 
in productiveness, and sometimes in the kind of ore, as they pass from 
one kind of rock to another. The grit rock of the Shav^rangunk moun- 
tains is overlaid by limestone,* and underlaid by the slate rocks of the 
Hudson river group. Both these rocks are, in general, more metalli- 
ferous than the grit rocks ; hence, the metalliferous veins of the grit, when 
traced into those rocks, or when the mines shall have been worked 
through the grit into them, may probably, be more productive. The 
limestone was not seen in place at Ellenville, but was observed at no 
great distance, both up and down the valley, parallel to the mountain, 
dipping in the same direction, and some sink holes, as they appeared to 
be, left no doubt on my mind, that the limestone ranged along the val- 
ley, between the canal and the base of the mountain, covered by allu- 
vial deposits. 
The Ulster mine near Red-Bridge, and worked by the North Ame- 
rican Coal and Mining Company, is situated on the Shawangunk moun- 
tain about one mile east of Red-Bridge, and six or seven from Wurts- 
boro', at an elevation of 600 or 700 feet above the valley. Two or three 
openings have been made. The first, which 1 believe is the uppermost 
one, I saw in 1837. It had been excavated during the preceding sea- 
son and winter. It was on a line of fault, where the fractured grit rock 
abutted against the broken, irregular and bent edges of the slate of the 
Hudson slate group. It seemed as though the slate rock had been 
elevated, and its edges by rubbing against the face of the grit, had been 
broken and bent very irregularly. The space between the slate and 
grit was filled with a silicious gangue containing quartz crystals in great 
numbers and of large size, more or less interspersed with masses of 
blende, galena, copper pyrites and common pyrites. In 1838 the com- 
pany had driven an adit level to intersect the vein at a depth of — feet. 
This level which intersects the strata of grit rock in a direction nearly 
perpendicular to their line of bearing, has been executed in the best 
manner, and is abundantly spacious, not only for drainage, but for tak- 
ing out the ore on the most extensive scale, should it be found in quan- 
tity. Some lead ore has been obtained from this mine, but the quantity 
* The limestone does not often cover the grit rocli on the sides of this part of the 
■ ountainSj but ranges along the valley, superposed in geological position. 
