Page:Popular Science Monthly Volume 69.djvu/423

Rh gigantic volcano. It exploded with such fury that one side became the finest dust and the other toppled over and now forms the channel through which the river is flowing." Much nearer to the truth than any of these explanations is that of Joaquin Miller. He suggests that the cañon is due to an underground river which worked away like the Green River has done in Mammoth Cave. Finally the roof fell in and behold the Grand Cañon. A picturesque explanation is Miller's and better than any of the others. Its truth consists in representing the river as the active agent, its error in the underground idea.

The geologist knows that the Colorado River cut out the whole cañon and regards the region as the finest example of river work on a grand scale in the world and as the type of all that is gigantic in displacement and denudation. The manner in which the river accomplished its tremendous task can be more easily comprehended by considering a number of facts; first, such as relate to the geography of the region; second, to its topography; third, to its stratigraphy and petrology; fourth, to its denudation and displacements. These different groups are closely interwoven with each other and the facts marshaled in one group are dependent upon those in all of the other groups.

Many tourists returning from the state of Colorado report that they have visited the Grand Cañon of the Colorado when they have simply seen the cañon of the Arkansas River—a cañon which would be a mere scratch in the side of the Grand Cañon. To see the chief cañon in the world they should have journeyed several hundred miles farther towards the southwest, to the region where a cañon 200 miles long has cut off the northwest corner of Arizona from the remainder of that state. Most tourists will now make their visit at the point called Grand Cañon Post Office, while the more fortunate ones will go east to Grand View and west to Cataract Creek. The railroad from the main line has been built to a well-chosen point where the cañon is a dozen miles wide and where for fifty miles to the east and west it is most gigantic and impressive. Within this region it displays all the salient points in its topography, succession of geological formations, different kinds of rocks, and erosion and sculpturing. So that one inquiring about the origin of the cañon can obtain all the factors to the answer in this locality.

Thanks to the good topographic map which the government has issued, one does not have to guess at the distances and depths in the region. One may refer to the map and not be disappointed. Accurate measurements do not rob the depths and distances of their magnificence, nor is exaggeration there necessary for impressiveness.

The new survey shows that the elevation of the plateau through which the river has carved its path is between seven and eight thousand feet above sea level. At the head of the cañon the elevation of the river is twenty-five hundred feet, and by the time it has flowed two hundred miles to the end of the cañon it is only a thousand feet