REVIEWS. 119 
become exposed to the action of air and water. In this way the solid nucleus of igneous rock 
became Garanin with a deep layer of disintegra ated snd wate — material, the 
ruins of its former e influence of heat from 
below and of air and water from above, the world of geologic and of —— history was to be 
volved. 
T4 +} 
t mperatures, develops ex- 
Wuordipary soivent powers; while from what has already been n of the influence of pre: 
tl ht of the overlying mass becomes a s 
— — Per the liquefaction of the wer portions of the sedimentary mate rim. TM is 
sind ose alternately wasting pie building : up continents. By the depression of the 
yielding crust bene vie 1 regions of great accumulation a ere follows a softening of the lower and 
of mime À more fusible strata, while the gre deer mass of more silicious -— becomes —€— into 
comparative rigidity. * and finally, as the result of he pee contraction, rises a hardened and 
— atas which Pn their composilion Fiela snoer these conditions the most liquid 
ti 
s conceived, th volcanic rocks. Shaa ccompanied by 
difficultly eóerethl iure they are eter extravasated a ong the fissures 
which form in the overlying stra d their The variations in the com- 
position of lavas and their didi ying gases m different regions , and even from the sam 
vent at different times, are strong confirmations of the trati e this view, kiss whieh may 
ee » harm that a the various f types of 1 " 
y the process of fusion." 
OLOGY OF COLORADO AND NEW MExico.* — With the small appropri- 
pere of ten thousand hie Dr. Hayden appears to have traversed in 
ad c 
for this purpose was so small that Dr. Hayden could not have accom- 
plished a large portion of his explorations without their assistance, The 
appropriation of ten thousand dollars, by the central government, to ex- 
plore two territories, while a state is spending annually more than twice 
that amount, per annum, upon a single institution, might excite some 
Ei dum and confusion in the minds of a foreigner 
route lay along the eastern foot of the Rocky Mountains, from 
due. in Wyoming Territory, to Santa Fé, the Middle Park having 
been explored by a lateral excursion from Denver City. Returning from 
e and 
ee the Rocky apogs through the South Park. The explorer's 
re with regard to the superficial deposits are very interesting, and 
hait ari importance as an explanation of the origin of some of the 
most interesting localities is our justification for the following extract: 
* Preliminary Field Report of the U. S. prada Survey of Colorado and New Mexico, 
By Dr. F. V. Hayden. Washington, D. C. 8vo. 
