Geology and Mineralogy. 69 
Trias has ae been ate denuded, and the Lower Trias nearl 
as much so. The erosion of the Carboniferous has bee n small, 
being sontnea ehiety to the cutting of cafions—most dotably- the 
Grand and Marble Cafions, which are sunk wholly in that series ; 
and in poe laces have ‘been cut through the entire Palmozoie 
series syste 
n the aaanaiia with regard to the nature of volcanic action 
re the origin of mountain disturbances, Captain Dutton rejects 
the idea of the earth’s interior liquidity, and holds that the theory 
of the earth’s contraction, as a cause of mov ys is inadequate 
to account for the facts. ” At the same time he a cknowledges erate 
tha of 
vith his remarks on the erosion in the Phaekd region, he queries 
whether the removal of 6,000 to 10,000 feet of rock material over 
so large an area would not “have disturbed the earth’s equili- 
u 
art of the loss by drawing upon its whole mass tic § 
further says that, to account fie ne uplifts as well, must 
almost necessarily oe to the operations of “ that item op plu- 
tonic force which seems to have been always at work and the ope- 
ce of which constitete the ‘aucckisnt and most momentous prob- 
m of dynamica geology ;” and also o “recognize the gL ayer 
of 1 that tendency, which indebitably exists within se sh 
maintain the statical equilibrium of its levels.” But t Fok 
during the very period of erosion, when feet in average 
depth was being removed (that is, after iden time), the moun- 
tain region ing an elevation of aye twice 6,000 feet. 
pei ylvania Geological Survey. The Geology of Mute 
County; by I. C. Wuire. Report No. QQQ. 234 pp. 8vo, with a 
colored geological map of the county and 119 vertical sections.—This 
Report is oceupied mostly with details respecting the strata and 
their coal beds, which pertain to the ‘‘ Productive Coal measures,’ 
the conglomerate measures underneath, and the sub-con lomerate, 
Th 
large bowlders over the top surface of the Drift, and also in the 
of it, leads the author to the conclusion that the transportation was 
not done by icebergs but by glacierice. The fact that these bowl- 
ders are limited in t their southward distribution in Western Pennsyl- 
