
Text printed on reverse of stereocard: WAR DEPARTMENT, CORPS OF ENGINEERS, U. S. A.<BR>Geographical EXPLORATIONS and SURVEYS WEST of the 100th MERIDIAN. No. 4. Grotto Spring, Grand Cañon, Colorado River. The water flows from the rocks above, and the umbrella-shaped rock about it is tufa, that has been formed by deposition from the mineral constituents of the water. The light spot seen through and beyond is the sand-beach of the river. Looking through this Grotta is seen in the distance the walls of the Grand Cañon, 3.500 feet in height on either side.