98 
ISOSTATIC THEORY 
in the so-called block-mountains of the Great Basin of Utah and 
Nevada. In fine, these mountains are regarded as huge fault- 
blocks floating on the soft interior of the earth much after the 
fashion of jammed ice cakes in a river at time of the Spring 
break-up. 
One does not gather from the writings of Dutton, Gilbert, 
Powell, Russell, or others of the extreme government experts and 
advocates of isostasy, that the basis of the hypothesis is not really 
so much the general impressions gained on the borders of the 
Great Basin as it is the revival of an all but forgotten idea first 
advanced by the English geologist Babbage and the astronomer 
Hershel, a hundred years ago, wherein it was postulated an in¬ 
sinking of the earth’s crust over areas of accumulating sediment. 
Now Captain Dutton, overpowered by the sudden realization 
of the tremendous volume of the erosion so clearly displayed on 
evjery hand in and about the High Plateaus of Utah and attracted 
strongly to Gilbert’s then recently proposed fault-block explana¬ 
tion of Basin Range structure, endeavors to reverse the long anti¬ 
quated suggestion of Hershel,- and argues for a rising of those 
tracts over which' depletion goes on vigorously. Therefore, it 
is urged that the more the mountain tops are removed the higher 
the elevations become. 
According to the Gilbertian conception of Basin-Range strucure, 
and the Dutonian idea of isostasy the fault-planes assumed as 
/ bounding longitudinally the mountain blocks should be lines of 
profound vertical displacement. These major ruptures should be 
the very ones of all others to reach down into the zone of plasticity, 
or rock-flowage. They should be belts along which there is re¬ 
lease of pressure sufficient to enable deep-seated molten magmas 
to reach sky. They should be gashes -along which mineralizing 
eflfects should be prominently and especially developed. On these 
narrow bands, also, chief ore-bodies should be situated. On these 
filled crevises principal mines should be’ opened. Their position 
should be marked by rows of shaft houses at the foot of every 
desert range. In reality none of these features seem to obtain. 
What is expected and what is actually found are notably con¬ 
tradictory. Mining operations are rarely discovered on the pied¬ 
mont scarp where plain meets mountain often as sharply as the 
strand-line of the ocean. Discrepancy between fancy and fact 
demands rigid inquiry. Should the fault-block idea of Basin 
