4 
: 
; 
i 
T DEA E = Ser ee won a Me E AAE a et eo 
GEOGNOSY OF THE APPALACHIANS. 465 
claimed that Hitchcock held a similar view. It will be seen that 
these geologists thus united in one group, the schists of the Hoosic 
range (regarded by Emmons as primary), with those of the Ta- 
conic range, and referred both to the age of the Champlain divis- 
ion, the whole of which was supposed to be included in the group. 
In the same address Professor Rogers raised a very important 
question. Having referred to the Potsdam sandstone, which on 
Lake Champlain forms the base of the paleozoic system, he in- 
— ‘Is this formation then the lowest limit of our Appalachian 
asses generally, or is the system expanded downward in other 
pnp by the introduction beneath it of other conformable sed- 
imentary rocks?’ He then proceeded to state that from the Sus- 
quehanna River, southwestward, a more complex series appears at 
the base of the lower limestone than to the north of the Schuylkill, 
and in some parts of the Blue Ridge he includes in the primal di- 
vision (beneath the Calciferous sandrock) “at least four indepen- 
dent and often very thick deposits, constituting one general group, 
in which the Potsdam or white sandstone (with Scolithus) is the 
second in descending order.” This sandstone is overlaid by many 
hundred feet of arenaceous and ferriferous fucoidal slate, and un- 
derlaid by coarse sandy shales and flagstones; below which, in 
Virginia and East Tennessee, is a series of heterogeneous con- 
glomerates, which rest on a great mass of crystalline strata. The 
accuracy of these statements is confirmed by Safford, who, in his 
recent report on the geology of Tennessee (1869), places at the 
base of the column a great series of crystalline schists, apparently 
representatives of those of southeastern Pennsylvania. Upon 
these repose what Safford designates as the Potsdam group, in- 
cluding, in ascending order, the Ovocee slates and conglomerates, 
estimated at 10,000 feet, and the Chilhowee shales and sandstones, 
2,000 feet or more, with fucoids, worm-burrows and Scolithus. 
These are conformably overlaid by the Knoxville division, con- 
sisting of fucoidal sandstones, shales, and limestones, the latter 
two holding fossils of the age of the Calciferous sandrock. It is 
noteworthy that these rocks are greatly disturbed by faults, and 
that in Chilhowee Mountain the lower conglomerates are brought 
on the east against the Carboniferous limestone, by a vertical dis- 
placement of at least 12,000 feet. The general dip of all these 
strata, including the basal crystalline schists, is to the southeast. 
The primal paleozoic rocks of the Blue Ridge were then by Rog- 
