Lesley.] 508 [April 21, 
the dip is low and the slates of No. III are thick, this line runs through 
the middle of our limestone valleys. Where the dips are steep and the 
Slate Formation No. III is not so thick, the latter forms the flank of the 
mountain, and the iron ore line runs at the base of the mountain. Where 
a closely folded anticlinal makes the valley so narrow that the two bases 
of the opposing No. III Mountains touch each other, and the ridge of the 
limestone formation No. II, juts up along the water course, or does not 
quite come to the surface (as in the three valleys at the left hand side of 
the above Section No. 8), the iron ore deposits must be abundant. 
Holding these simple principles of structure in mind, it is evident that 
the great iron bearing formation, at the base of the No. IIT Slate Forma 
tion, keeps its character all through Middle and Southern Virginia, and 
will be as rich and certain a basis for large iron mining and iron 
smelting operations as any other and better known section of the Appa- 
lachian Mountain Belt between New York and Alabama. 
An old forge at the west end of Paint Lick Mountain (between Leba- 
non and Jeffersonville) used this top-limestone-horizon ore ; and I have 
no doubt of its abundance in many other places. It is more con- 
stant and regular than the ores further down and near the bottom of the 
Limestone Formation No. II. And these, moreover, are often swallowed 
up to such a depth by the downthrows as not to be attainable for many 
years. ‘ 
It remains to notice a quite different variety of iron ore, which, I hope, 
will prove sufficiently abundant at a few points along your line of road. 
It is the Fossil Ore of V ; the Paint or Dye-stone Ore of Tennessee. 
To describe the situation of this ore, I must refer to the map accom- 
panying this paper. I have colored Formation No. V, the red shales of 
the Clinton Group, with the color which I gave it on the State Geological 
Map of Pennsylvania. This color, however, is not appropriate to the 
formation in Southern Virginia; for the red soil and reddish (Upper Si- 
lurian) sandstones which mark the slope sides of our Pennsylvania Moun- 
tains (of No. IV), gradually disappear as one goes south from the Poto- 
mae, giving place to a gray soil and very slightly, often not at all, red- 
dened sandstones and slates. On the other hand, the opposite side of the 
mountain, where the basset edges of the (Lower Silurian) slates of No. 
III crop out, is very red. A Pennsylvanian geologist floating over the 
country in a balloon would naturally make the mistake of just reversing 
the geology of the mountain, and would descend upon the wrong side of 
it to seek for the well-known and highly prized fossil ore bed of Danville 
and Frankstown. 
In spite of this change of color in the formation soils of the region, I 
have thought it best to retain the red color for No. V upon the map, see- 
ing that it represents the blood-red color of the fossil ore itself. One may 
see, then, by tracing the lines of color on the map, where the fossil ore 
bed ought to be; whether it be there or not. Very extensive and costly 
explorations have been necessary in Pennsylvania and Maryland. No 
doubt much research of the same sort will be called for in Virginia. But 
the ore is there ; and, as in Pennsylvania and Tennessee, it will run for 
