JAMES DWIGHT DANA. O12 
nized, not only long periods of sedimentation and accumulation 
of strata in synclinoria, but separating these periods of quiet 
there were revolutions resulting in each case in lifting greater or 
smaller areas permanently above the surface of the ocean, and 
the later of these revolutions were the grander, in amount of ele- 
vations and mountain making, in fracturing and lava outflows, 
and in production of volcanoes, because, as his theory explains, 
of the greater thickness and rigidity of the crustal portion of 
the earth incident to the secular cooling of the globe. 
In the article of 1847 the Appalachian revolution closing the 
Paleozoic, and what has been subsequently called the Palisade 
revolution, which terminated the Jura-Trias of the Atlantic bor- 
der region, are distinctly referred to; and besides these we now 
know of the Taconic revolution, at the close of the lower Silu- 
rian; the Acadian revolution terminating the Devonian in the 
east; the great Rocky Mountain revolutions terminating the 
Mesozoic and bringing in the Tertiary conditions in the Lara- 
mide elevations, progressing a stage fartherin the lifting of the 
Coast Range region at the close of the Miocene, and finishing its 
work at the close of Pliocene in the lifting of the Sierra Nevadas. 
That these more or less catastrophic events were the natural con- 
sequences of the continuous uniform cooling and contracting of 
the crustal portions of the globe, is a corollary of Dana’s theory 
of the earth. As he observed, referring to these revolutions in 
the last edition of the Manual, ‘‘the above facts are brought for- 
. ward to illustrate the grand principle, already admitted by some 
writers, that such grand crises,—by causing wide emissions of 
heat and changes of level in the sea, and violent shakings of 
the globe with its mobile waters, —were in early times a neces- 
sary result of the contraction in progress.” 
Referring to the Appalachian revolution, he wrote, ‘‘It is not 
a matter of surprise that there should have been an abrupt ces- 
sation with this event of preéxisting forms of marine life. The 
period when the effects of dislocation began to be transferred 
from the oceanic areas to the continents appears to have been 
the era of this catastrophe, and it was an era of similar changes 
