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Show THE AWAPA PLATEAU. 275 ing range in the superficial aspects of the beds. In the northern part of the plateau the dark argilloid and hornblendic trachytes predominate. They agree in their characters and aspects with those which occur in the Fish Lake Plateau and Mount Marvine. There is also decided evidence that the main sources from which they outflowed were around the southeastern borders of the lake. This evidence is substantially the fact, that the sheets increase in thickness and become more rugged in that quarter, and all the phenomena of flow indicate movement from that direction. The supposed location of the vents, however, was not visited. No augitic andesites were noticed intercalating with the northern trachytes of the Awapa, though large bodies of them may have escaped observation, owing to the superficial and cursory character of the investigation. No conglomerates or tufas were seen in the northern part of the Awapa, and these would have been noticed if they really exist there in masses of any importance. As such bodies are usually very bulky and conspicuous, it is hardly possible to overlook them. In the western part of the plateau, however, they are found in great volume. They are stratified in the usual manner, with nearly horizontal bedding or with that peculiar cross-bedding which may be seen in Panquitch Canon (Heliotype No. 4). In the western wall of the plateau, a little north of East Fork Canon, these conglomerates form a grand cliff and talus rising about 3,400 feet above Grass Valley, and the total thickness of the fragmental beds is roughly estimated at 1,600 feet. Large masses of hornblendic trachyte are found beneath them, and granitoid trachyte above them. These beds of conglomerate stretch north and south from this point, forming the, most conspicuous part of the plateau wall, for a distance of 21 or 22 miles. Their degradation gives rise to a precipitous escarpment, broken in several places by ravines and gorges. They are also found in great bulk in the canons which cut into the heart of the plateau. They are believed to be alluvial in their origin. The fragments which they contain are exceedingly varied in their composition and texture. Hornblendic andesites and trachytes are commingled in the same stratum, and of each kind there are very many varieties. In one of the deeper canons some propylitic fragments were found, but |