78 
As already stated, the narrower and more rugged parts of the 
Royal Gorge are cut in the harder rocks. This fact is well illus- 
trated near the Hanging Bridge, for here the walls are vertical be- 
cause the great joint cracks that cut the granite are vertical. When- 
ever a piece of rock is split from the walls it breaks off along one of 
these vertical joints, and the stream has difficulty in undermining 
a wall that is composed of huge blocks of rock set on end or rather 
that have one end deeply buried below water level. The great open 
fissures along some of these joints give picturesque detail to the 
walls; the best known fissure is one on the right that can be seen 
to advantage by looking back just after passing the Hanging Bridge. 
This crack is 20 feet wide, and down it flows a stream of water which 
in the driest season yields cool water to the thirsty traveler who may 
be enjoying a tramp through this great highway. The traveler will 
doubtless see many other cracks almost as strongly marked as this 
one at different places in the canyon walls. Many of these fissures 
have been cleaned out by small streams of water, leaving crevices 
only a few feet wide, which in many places slope under the over- 
hanging rock for long distances.” f 
GUIDEBOOK OF THE WESTERN UNITED STATES. 
** Doubtless many persons who have 
passed through the Royal Gorge have 
wondered what agent produc 
deep and narrow cleft. The question 
‘pe 
reply. If it is a geologist he will say 
that the river has excavated the can- 
yon, cutting away the rock grain by 
grain; but if the sauhtlaas is answered 
by one who has not made a study of 
such problems he will probably scout 
such a proposition and say that it is 
impossible for a river to cut a. hard 
rock like nes gneiss and Bom the 
gorge is due great e that 
S opened sy an earthqu ena This 
view is most commonly held by those 
who are unfamiliar with the work of 
streams and was even held by many 
geologists less than a century ago. 
t is comparatively easy to prove 
that the Royal Gorge was not formed 
y an earthquake, for, first, the gorge 
this | 
is too crooked to be the result of a 
and, second, the bands of rock 
ean be traced practically from wall to 
ch 
wall across the canyon. There is 
possibility of a break aves as would 
be required by the earthquake hypothe- 
yp 
sis. Altogether the evidenss is con- 
clusive that the Royal Gorge and most 
other canyons are not earthquake fis- 
sures a were cut by the streams 
that oce them. 
The soe power of water depends 
n the amount of sand and gra 
ing action of the grains of sand on the 
ocks over which the water flows. It 
acts much like a sand blast, and no 
rock is so hard that it can withstand 
peration, d 
and night, and Mauch it will pe 
its work apparent. 
