^54 MILLSTONE GRIT. 
from clay slate by being an aggregate of mineral 
particles, instead of being wholly made up of a sin- 
gle mineral species. These two rocks alternate 
with each other without any determinate order. j 
They sometimes lie below as well as above the coal 
measures, as will appear by examining the sections 
above given. This group is sometimes very rich 
in metallic ores, such as lead, copper, mercury, ; 
iron, zinc, and manganese, which occur in detach- 
ed spots, in nodules or beds, but never in veins, | 
"We also find in the grit phosphate of lime, fluor 
spar, sulphate of baryta, &c. 
In Whitely county, Kentucky, the millstone grit 
is cut through by the Cumberland River to the depth 
of 700 feet; the conglomerate part being about 500 
feet thick, and the shale, with three horizontal good 
veins of bituminous coal, each from three and a 
half to four and a half feet thick, being about 200 
feet. Near Cumberland there is a fine exhibition 
of this rock, in an escarpment between 800 and 900 
feet high. The millstone grit also abounds in the ^ 
State of New- York, and we find it throughout Her- i 
kimer and Oneida counties, with a thickness of 30 
or more feet. It seems to be composed of rolled 
stones or pebbles, and the brine-springs lie above it. 
It may be stated, then, as a general fact, that the 
Blue Ridge System contains no coal ; the Appalach- 
ian System contains the anthracite ; and the Alle- 
ghany the bituminous coal measures, which also 
spread to the west over an immense area, and are 
traceable, as a single geological formation, far be- 
yond the Mississippi. 
Mr. R. C. Taylor, a practical engineer and geolo- 
gist, has offered some considerations to show that 
it is very improbable, as Mr. Featherstonhaugh and 
others expect, that coal will be found in any quan- 
tity in the State of New- York ; and Mr. Hildreth 
remarks that, with the exception of the Susque- 
hanna and its tributaries, and Will's Creek, emp- 
