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GUIDEBOOK OF THE WESTERN UNITED STATES. 



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. ^^ 



'° Doubtless many persons who have 

 passed through the Royal Gorge have 

 wondered what agent produced this 

 deep and narrow cleft. The question 

 may not often have been voiced, but 

 scarcely anyone can see a chasm so 

 tremendous without wondering how it 

 was formed. The answer which the 

 traveler will get to such a question 

 depends upon the person making the 

 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 question 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 this gneiss and that the 

 gorge is due to a great fissure that 

 was opened by an earthquake. 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. 



It is comparatively easy to prove 

 that the Royal Gorge was not formed 

 by an earthquake, for, first, the gorge 



is too crooked to be the result of a 

 fissure and, second, the bands of rock 

 can be traced practically from wall to 

 wall across the canyon. There is no 

 possibility of a break such as would 

 be required by the earthquake hj'pothe- 

 sis. Altogether the evidence is con- 

 clusive that the Royal Gorge and most 

 other canyons are not earthquake fis- 

 sures but were cut by the streams 

 that occupy them. 



The cutting power of water depends 

 on the amount of sand and gi-avel 

 which the stream is able to carry or 

 to roll along on its bottom. Clear 

 water may dissolve the rocks, but it 

 has no cutting power. Water loaded 

 with sand cuts the rocks by the scour- 

 ing action of the grains of sand on the 

 rocks over which the water flows. It 

 acts much like a sand blast, and no 

 rock is so hard that it can withstand 

 the constant grinding of grains of 

 sand. According to human standards 

 the process is very slow, but it is 

 ahnost constantly in operation, day 

 and night, and eventually it will make 

 its work apparent. 



