AMERICAN NATURALIST. 
4 
a 
I Vou. xxi. NOVEMBER, 1887. No. 11. 
_ THE MATERIALS OF THE APPALACHIANS. 
é BY Ei W. CLAYPOLE, AKRON, OHIO. 
PENNSYLVANIA consists almost entirely of massive palæ- 
ozoic deposits of sand and shale with a few limestones. 
These beds united reach a thickness greater than do those of the 
same age in any other known part of the world. Reasonably 
accurate measurements have given them a total depth in some 
Places of thirty thousand to forty thousand feet. Westwardly 
i they thin off, and on the Ohio line scarcely reach one-fourth part 
a of this enormous depth. ; 
All geologists are agreed that this immense mass of sediment 
Was deposited on the slowly subsiding bottom of the eastern part 
3 of an ocean covering the whole interior of North America,—the 
, North American palzozoic ocean, as‘it may be called for conve- 
q mence, The extent and form of this ocean varied considerably 
-different times during its long existence, but taken as a whole 
: it was uninterrupted sea. r 
& Itis further a geological truth, so evident as to be now axio- 
: ta that all this vast mass of palzeozoic deposit was obtained 
fe es 
tion ig ion from some contemporaneous palzozoic land. Deposi- 
; of implies erosion to a precisely equal amount. For every ton 
has he. _ Mud deposited on the sea-bottom an equivalent ton 
as been removed from some land-surface. Sediment is "e 
“a It is only removed. Hence all these huge Appal achan 
from which the mountains have been since carved imply the 
a uction of exactly equal masses of some more ancient jase 
VOL. XX1.—wo, 11, 65 eae 
