During July 1909, Dr. Cummings formulated plans to set out in search of the bridge. There were delays in obtaining the necessary guides. In the meantime, Dr. Cummings received word that W. B. Douglass, a Government surveyor, was en route to the area also to look for the arch. Subsequently, the Cummings-Douglass parties met and joined in the search for the Nonnozoshi, which was the Navajo word for the great stone arch. The journey lasted several days. The party crossed canyons and “slick rock” surfaces where the horses slipped and skidded. Frequently, it was necessary to retrace portions of the course, because forward progress was blocked by “rimrock” ledges which the horses were unable to cross. There were more canyons, some with dry, boulder-choked beds, others with water and dense brush. Across a scrub juniper (cedar) flat, and down into the last canyon they went. This was Nonnezoshi Biko, the Indian guide’s name for the canyon of the great stone arch, or Rainbow Bridge Canyon of the present. The horses, as well as the men, were fagged because of the hard trail and shortage of forage and water. The footsore procession trudged forward; and in the late afternoon of August 14, 1909, the party rounded a bend in the canyon, and Dr. Cummings became the first white man to see the largest and most beautiful of all known stone arches, Rainbow Bridge. [Illustration: _How a natural bridge is formed_] _HOW WAS IT FORMED?_ Geologists tell us that, at the time of the formation of the rocks from which Rainbow Bridge was later carved, the physical environment of that vicinity may not have differed greatly from much of the present Southwest. Broad valleys surrounded by highlands were present. Run-off from rainfall in the highlands brought great quantities of gravel, sand, and mud, which were spread as horizontal sheets over the floors of the valleys. Locally there were shallow lakes. Mud and sand were deposited in the lakes, and evaporation of the water produced limy and gypsum-filled muds. These sediments were compressed by being deeply buried to form the layers belonging to the Kayenta formation, part of which is the thin-bedded stratum exposed in the canyon beneath Rainbow Bridge. Following this period of deposition, there was a changed environment during which sand accumulated until it was several hundred feet in thickness. It was deposited in curved cross-bedded layers in dunes, later to be blown away and redeposited again and again. This produced a complex system of cross-bedding throughout the entire formation. In time, a blanket of other rock materials was deposited by wind and water over the shifting sand. Percolating water, with lime and gypsum in solution, aided in making the material firm and hard to form what has been named the Navajo sandstone.