106 
ISOSTATIC THEORY 
The direction of fault movement is commonly more nearly 
horizontal than vertical. Contrary to usual assumption dislocative 
phenomena of this kind are seldom upright and gravitational. 
When carefully analysed the direction of the slipping is found to 
be very nearly on the level. Associating this feature with the 
high dip a warped surface is obtained the component forces of 
which are capable of exact mathematical expression and ready 
reference to the major telluric stresses imparted by the earth's 
rotative retardation. 
Thus is emphasized the fundamental weakness of the mathemat¬ 
ical theory of isostasy since no distinction is made between the 
physical behavior of the thin crustal shell of rock-fracture under 
telluric stress and of the thick interior mass responding to rock-flow. 
In view of the fact that any depression, or in sinking, of the crust 
due to sedimental loading occasions removal of an equal thickness 
from the bottom of the affected prism through direct flowage it 
may be questioned whether any such rock-prism appreciably 
changes its specific gravity, so slightly in this respect do rocks in 
the zone of fracture differ from one another. What really then, 
is mistaken for floatage phenomena is adjustment in the earth’s 
crust of the effects of centrifugal force arising out of a retar¬ 
dation of rotation of the geoid. 
From the miner’s viewpoint it is, after all, not so strange that 
the Basin Ranges and the Rocky Cordillera should on the one hand 
so strongly belie the verity of isostasy insofar as they are directly 
concerned, and on the other hand should point so conclusively to 
the strictly telluric nature of their genesis, and indeed of orogeny 
in general. 
Referring, then, characteristic mountain tectonics with which 
we are best acquainted to the secular diminution in rate of the 
earth’s rotation all of the principal orographic features are readily 
and satisfactorily reproduced artificially. When, also, it is fully 
realized that mountain genesis appears to be merely feeble expres¬ 
sion of the larger telluric properties of our globe we may readily 
adjust the dependent structures, including fissure-veins, so that 
search for new ore deposits shall have scientific basis, and the 
long sought desideratum of predictable results. 
