No. 200,J 
291 
facilities for geological investigation. In all cases where there are al- 
ternations of hard and soft, or shaly strata, we have fine natural sections 
along the river. Where there is a considerable extent of shaly strata, 
the banks are low and rise more gradually from the river. In such 
cases we can readily obtain a knowledge of the character and contents 
of the rock by tracing the small tributaries, which having less wearing 
force, commonly descend in a succession of rapids and cascades to the 
level of the river, thus affording ample opportunities for the most mi- 
nute investigation. 
I have already observed, that the direction or bearings of the rocky 
ranges is nearly east and west, and their dip to the south or southeast. 
The direction and amount of dip has been generally overlooked, or con- 
sidered as unimportant, and for a short distance it may be scarcely per- 
ceptible, though it amounts to 50 or 60 feet in the mile, or about one 
degree. In some places the amount of dip is much greater for short dis- 
tances. 
I consider the rocks of the 4th District as belonging to the old red 
sandstone and the carboniferous groups, and to be above the Silurian 
system of Mr. Murchison. The evidence for this conclusion rests, in 
part, upon the organic remains, and if we can rely on these characters, 
there appears little question regarding the age and position of our rocks. 
The trilobite has never been found in any formation newer than the 
carboniferous, though it occurs in rocks much lower in the series. In 
our district the trilobites terminate with the rocks marked in the section 
as the shales of the carboniferous limestone. In the slates, sandstones 
and thin beds of limestone above this point, I have never seen a frag- 
ment of a trilobite. 
The Calymene Blumenbachii, or Dudley trilobite, occurs abundantly 
in a dark blue limestone, somewhat resembling the mountain limestone, 
but below the red marl and sandstone represented in the section. That 
part of the marl and sandstone seen in the 4th District contains few 
fossils, except Fucoides, but the whole of the formation has not been 
examined. 
In the shales above the sandstone we find several species of trilobites: 
The Calymene, macropthalma, C. bufo, C. Blumenbachii, Asaphus cau- 
datus, Paradoxides Boltoni, Trimerus delphinocephalus. 
The bituminous limestone and the gypseous rocks rarely contain tri- 
lobites, but the carboniferous limestone, and the associated shales con- 
