The working hypothesis to be presented deals with the middle and southern portions of the Rocky Mountain region within the United States. In this area there are between fifteen and twenty somewhat distinct ranges, and if all local names were used the number would be still larger. These ranges may all be classed in the group of young, rugged mountains. Many of the crest-line peaks in the bolder mountain chains rise to elevations over 14,000 feet. They are sharp and picturesque, and many of them have not as yet been climbed.
For more than a century this mountain region has attracted explorers, mountain climbers, lovers of the primitive landscape, prospectors, and ranchmen. For fully half a century, scientists have frequented the area. Soon after the close of the Civil War, King, Hayden, Wheeler, and Powell organized and conducted important expeditions into portions of the area. The studies of these . . .