No. 384.] JAMES HALL AND AMERICAN GEOLOGY. 895 
remains speak either of a quiet sea or deep water, where they 
were placed beyond the tumult that might have raged nearer 
the surface.” 
Hall’s study of this succession, and the generally increasing 
thickness of deposits to the east along the Appalachian uplift, 
his generalizations upon the continuity of these beds westward, 
and his growing realization of successions of fauna, with more 
or less clear appreciation of local variations in fauna, were 
resumed in the interesting and able introduction to vol. 
iii of the Mew York Paleontology (1859). The fact of the 
preponderant accumulations of sediment along the Appala- 
chians had been reviewed and studied by him with an increas- 
ing certainty of divination that the association of these heavy 
deposits with the mountain chain itself was in the nature of a 
causal connection. 
Hall had apprehended with his usual power of appreciative 
insight the dissertation of Herschel on the mobility of the 
earth’s crust, and it was an exhibition of hermeneutics in geo- 
logical science which read into the facts of the Appalachian 
tumulus the specific applicability of the suggestion. Here he 
saw a continental ridge made up of sedimentary rocks, twisted 
and folded, to be sure, and showing the results of powerful com- 
pression. But the mass, the vast aggregate of its limestones, 
slates, and sandstones, was sedimentary, and these deposits 
were evidently concentrated along a meridional crease, a trough 
or depression secularly raised and lowered. This path of sedi- 
mentation against and over an oscillating shore line provided 
the material, when raised, for a mountain chain. The trough 
was itself an inverted mountain ridge, and nowhere else was 
there such an adequate supply of mass to create an imposing 
elevation when lifted. As Hall succinctly said: “ At no point, 
nor along any line between the Appalachian and Rocky moun- 
tains, could the same forces have produced a mountain chain, 
because the materials of accumulation were insufficient ; and 
though we may trace what appears to be the gradually sub- 
Siding influence of these forces, it is simply in these instances 
due to the paucity of the material upon which to exhibit its 
effects. The parallel lines of elevation, on the west of the 
