go farther up the gorge; but we [50] Could not go far, for 225 yards ad- vance brought us to the foot of a pre- cipice estimated to be 300 feet high, forming part of the walls of a basin in the stream bed which was 80 yards long by 50 yards wide. The floor of this basin is 620 feet above the sea. The upper part of the precipice is composed of a heavy lava flow which is inclined at a low angle down the gorge. The lower part of the flow is flatter, the upper part roughly columnar in structure. The major portion of the section given by the precipice is unsorted tuff, showing slight indications of aerial bedding. Lines of sand on the walls of the basin some of the show stages passed through in the tilling and excavation of the gorge. [del. xxii, 71 B]