ee 
J. D. Dana on the origin of the Earth’s Features. 207 
tains themselves. At no point, says Mr. Hall, between the Appalachians 
and the Rocky Mountains, could a mountain chain have been roduced, 
because the accumulated materials were insufficient. The Rocky Moun 
tains owe their greater height to a series of later deposits than ri: 
3 which cap the Appalachians; the White Mountains are covered with a 
3 later formation than that which covers the Green Mountains; the Alps 
are newer than the Jura; and, generally, if it is the original deposition 
of the materials that has pro uced mountains, then the greater the accu- 
terially from other mountain ranges.” If t E eeiainrneiie oe of the 
Alps are of Paleozoic age, and the sequence has _been continued, even 
the long-continued accumulation of sediments; sediments not simply 
marking this altitude, but vastly more, for there is doubtless as much oj 
the mass below the level of the sea as above it. This view we find a 
plicable to the Appalachians, and it must be a necessary condition of 
mountain elevation.” ——Hall’s Pal. N.Y., Vol. LII, Introduction. 
“We must look to some eae _— than heat for the production of 
the phenomena [of metamorphism]; and it seems that the prime cause 
must have existed within tha material itself, and that the entire change 
is due to motion, or fermentation, and pressure, aided by a moderate in- 
ass to 
a level where the surrounding temperature was higher.— 
The hypothesis then is that the thickening of the deposits 
along the Appalachian region to 40,000 feet, more or less, which 
went on through the Paleozoic ages (and which was due mainly, 
as Mr. Hall holds, to material distributed e the northeastern 
Oceanic current, now she co abrador current) ultimated in a 
subsidence of 40, 000 feet, and in flexures, plications, fractures, — 
metamorphism, trap dikes, and mountains; and that the same 
general principle was exemplified in the origin of the 
mountains and An aon the Alps and Himalayas, and all other 
mountain =. 
- The fact of | A " subsidence in the Appalachian region ac- 
mpan, aes the accumulation of the deposits is established by 
ssliste ccs markings in most of the successive strata, from 
the bottom to the top -of the Paleozoic, as stated by Pr ofessor 
4 
