The completion of the geological history of the Sierra Nevada and associated ranges appears to rest, for practical reasons, upon the determination, at different times and in different places, of the necessary facts. It is with this in mind that the writer presents the following data, ascertained on a recent short business trip. It is hoped that others may be fortunate enough to be able to dig more deeply into the rocks, both in the locality described and elsewhere in the adjacent regions. The

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... so Range lies between the Sierra Nevada on the west and the Darwin or Argus Range on the east, separated from each by a long narrow valley. At the north end the Coso Range forms the south boundary of Owens Valley, and extends thence southerly along its main axis for about forty-five miles. The greatest width at the north is twenty miles (see map, Fig. i) . A number of general statements have been made regarding this peculiar range, with but little in detail. From whatever point of view seen, the Coso Range is strikingly different in appearance from the surrounding mountains. Fig. 2 shows the Range looking south from Keeler. The typical appearance is here well outlined. The flat, nearly horizontal, sky line, with, in general, gentle slopes to the bordering valleys, give an air of maturity not found in the precipitous fault scarps of the Basin Ranges. One comparatively small scarp is seen in the eastern part of the range, facing northeast, and its supplementary scarp occurs in the western portion. The form of the whole is that of a very flat elliptical dome, with its longer axis lying north and south. The periphery of this dome grades into the surrounding valley alluvium. The northern and western flanks are largely covered with basalt flows; the eastern 64 This content downloaded from 129.049.005.