The granite walls of the Grand Canyon bear innumerable veins, but as prospecting is there so difficult it will be many a long year before the best are found.

The search for mineral veins has done much to make the farther parts known, just as the earlier search for beaver took white men for the first time into the fastnesses of the great mountains, and earlier the effort to save the souls of the natives marked their main trails into the wilderness.
This sketch of the Basin of the Colorado is most inadequate, but the scope of this volume prevents amplification in this direction.

These few pages, however, will better enable the reader to comprehend the labours of the padres, the trappers, and the explorers, some account of whose doings is presented in the following chapters.* * In connection with the subject of erosion and corrasion the reader is advised to study the following works, which are the standards: The Exploration of the Colorado of the West, and the Geology of the Uinta Mountains, by J.W.

Powell; The Henry Mountains, by G.K.

Gilbert; The Geology of the High Plateaus of Utah, and The Tertiary History of the Grand Canyon District, by C.E.