208 J. D. Dana on the origin of the Earth's Features. 
Hall. And it must be admitted, further, that in other regions 
of the globe subsidence has, in most cases, attended similar 
accumulations. We do not question this postulate of Mr. Hall’s. 
The Carboniferous formation of Nova Scotia is a case o 
kind where the evidence is clear; for although 16,000 feet thick, 
it bears throughout proofs of its origin near the ocean’s level, 
in dirt beds, coal seams, estuary deposits, and the like. The 
16,000 feet of thickness prove, therefore, 16,000 feet, approxi- 
mately, of gradually progressing subsidence. 
should be the thickness of the earth’s rocky crust, and what its 
density, in order that it should be thus sensitive to the touch of 
sediments? Could there be the foot-per-foot movement under 
any degree of thinness? Surely the 800 miles of the mathema- 
ticians, or the densely viscid or the solid interior of some theorists, 
would give it no chance. And would a thickness of twenty 
les, or of ten, or of five, allow of this no-resistance move- 
ment? The idea is obviously opposed to the very nature of the 
earth and its forces, 
(2) pressure upon the interior liquid mass of the globe, which 
would be felt variously over the whole inner surface of the she 
* For details on this point, see Dr. Dawson’ paper in the Jour. Geol. Soc. of 
London, No. 86 (May, 1868), p- 95. . . 
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