On the Bristol Copper Mine. 363 
TRANSVERSE SECTION OF BRISTOL COPPER MINE. 
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greatest drawback on the prosperity of the mine, since the ore 
ground was too wide to be all taken down by the miners, and the 
distribution of the branches of ore in it was too irregular to admit 
of their being found without occasional expensive excavations in 
dead ground. In general, throughout the mine, a tendency to a 
concentration of the ore around the masses of granite ma 
marked, and the latter are not unfrequently well filled with strings 
and bunches of ore, especially near their exterior. 
he limits of the ore-ground to the west, or in the direction of 
the older rocks, the sandstone being to the east of the contact- 
