These Shamans and cult societies have a great variety of functions to perform. All disease and all injuries are attributed to mythic beings or to witchcraft, and on these pathologic ideas the medicine practices of the people are based. The medicine men are sorcerers, who work wonders in discovering witchcraft and averting its effects or in discovering the disease-making animals and overcoming their power. So the Shamans and the cult societies are the possessors of medicine and ceremonies designed to prevent and cure human ailments. They also have charge of the ceremonies necessary to avert disaster and to secure success in all the affairs of life in peace and war; and they prescribe methods and observances and furnish charms and amulets, and in every way possible control human conduct in its relation to the unknown. No small part of savage life is devoted to cult ceremonies and observances. The hunter cannot penetrate the forest without his charm; the woman cannot plant corn until a ceremony is performed for securing the blessings of some divine being. Religious festivals and ceremonies are carried on for days and weeks. A war must be submitted to the gods, and a sneeze demands a prayer. Our arrival at Fort Wingate practically ended the exploration of the great valley of the Colorado. This was in 1870. In 1891 we can look back upon the completion of the survey of all of that region, for it has now been carefully mapped. The geology of the country has been studied, and the tribes which inhabit it have been subjects of careful research. This work has been carried on by a large corps of men, and interesting results have accrued. 365 powell-canyons-231.jpg ASHTISHKEE, A NAVAJO CHIEF. 366 powell-canyons-232.jpg NAVAJO MEDICINE LODGE, VIEWED FROM THE SOUTH. 367 powell-canyons-233.jpg NAVAJO MEDICINE LODGE, VIEWED FROM THE EAST. 368 powell-canyons-234.jpg NAVAJO FIRE DANCE. 369 powell-canyons-235.jpg WORKSHOP OF NAVAJO SILVERSMITH. 370 powell-canyons-236.jpg ZUÑÍ WOMAN WEAVING A BELT. 371 powell-canyons-237.jpg WEAVING OF DIAMOND-SHAPED DIAGONALS. 372 powell-canyons-238.jpg ZUÑI FETICHES. 373 powell-canyons-239.jpg EFFIGY POTTERY FROM ZUÑI. 374 powell-canyons-240.jpg ZUÑÍ POTTERY. 375 powell-canyons-241.jpg ZUÑÍ GRAILS. 376 powell-canyons-242.jpg CULINARY POTTERY FROM ZUÑI. 377 powell-canyons-243.jpg NAVAJO FABRICS. 378 powell-canyons-244.jpg THE GRAND CANYON. 379 CHAPTER XV. THE GRAND CANYON. THE Grand Canyon is a gorge 217 miles in length, through which flows a great river with many storm-born tributaries. It has a winding way, as rivers are wont to have. Its banks are vast structures of adamant, piled up in forms rarely seen in the mountains. Down by the river the walls are composed of black gneiss, slates, and schists, all greatly implicated and traversed by dikes of granite. Let this formation be called the black gneiss. It is usually about 800 feet in thickness.