igS The Amenca?i Geologist. March, i895# 
The Richmond Folio .--Folio 46, U. S. Geological Survey, i8gS. 
Geology by Marius R. Campbell, assisted by Joseph A. Taff and 
Walter C Mendenhall. 
This folio, just issued, the first to treat of an area entirely within 
the limits of Kentucky, is uniform in plan and character with the other 
folios dealing with the geology of the southwestern Appalachian prov- 
ince. 
The quadrangle, 944.2 sq. mi. in extent, and bounded by the parallels 
"f 37° 30' and 38° and the meridians of 84° and 84° 30', has Richmond, 
the county town of Madison county, very nearly in the center. The 
quadrangle includes, besides Madison, parts of the surrounding coun- 
ties of Clark. EstiJl, Jackson, Rockcastle, Garrard, Jessamine and 
Fayette. 
The discussion of the topography affords Mr, Campbell (an ardent 
"peneplainist") an opportunity to interpret the relief features in the 
southwestern Appalachians and adjacent regions to the west in ac- 
cordance with the advanced views of the now dominant school of 
American physiography. 
Evidence of two peneplains of different ages — the one provision- 
ally considered Cretaceous and the other Eocene — is found within the 
limits of this quadrangle. The facts and arguments here so clearly 
and forcibly presented, constitute a valuable contribution to physio- 
graphic geology. To a few geologists, however, who are still doubt- 
ing Thomases as regards this doctrine of oft recurring peneplains, the 
evidence of more than one cycle of erosion in this region may appear 
inconclusive. Some doubtless will still prefer to explain these plains 
or plateaus, (there are really more than two — one for every marked 
lithological change in formation) lying at different levels and dis- 
sected, as but the expression of atmospheric denudation acting through 
one long cycle of erosion upon rock formations, differing in hardness 
and other characters. The successive geologic age assigned these 
plains in accordance with the peneplain theory may be granted, if we 
are allowed to understand that it is net age at whfch a certain stage 
in an erosion cycle was reached that is meant; but age during which 
topographic features were determined by exposing to erosion fresh 
rock surfaces differing in character from that which had to be denuded 
in order to bring these new surfaces into view. Accordingly we are 
inclined to see in Mr. Campbell's "Cretaceous peneplain" in Kentucky 
Carboniferous strata, afterwards elevated and now found 500 feet above 
the Lexington or Eocene peneplain, simply the remnant of what per- 
haps as late as Cretaceous time was a continuous sheet of fairly homo- 
geneous strata lying well up upon or over the Lexington dome; and 
by the "Lexington Eocene Peneplain" we are disposed to understand 
an area of Silurian rocks which began to be uncovered and to attain 
a considerable extent during Eocene time. 
That the whole country in question was once reduced by denudation 
to a relatively low level — base leveled if you please — there can be little 
question. Mr. CampljcH's rcviev,- of the evidence upon which this con- 
