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Rocks of Southern California.—Hershey. 289 
At mile-post twenty from Barstow, there appears from 
under the Quaternary gravel, a limited area of hard, massive, 
ght gray rock of very fine texture and non-committal appear- 
ance. Under a hand microscope it appears like a very fine 
quartzyte or a felsyte. Certain characters suggest a highly 
metamorphosed novaculyte, but it is more probably an altered 
old rhyolyte. 
One-half mile east of Helen station (mile-post twenty-one), 
there is a black rocky hill rising prominently above the Quater- 
nary gravel deposit. It is composed of the above fine-grained, 
white and light gray rock stained black on the surface. In 
belts it is schistose from shearing. There is some greenstone 
in connection with it. It becomes coarse-textured in one local- 
ity and is evidently at this place a metamorphosed fragmental, 
apparently an old rhyolyte tuff. Angular white fragments 
are abundant. Probably the mass of the rock is a fine rhyolyte 
tuff with some rhyolyte sheets. It is a much older series than 
the Tertiary rhyolytes so strongly developed on the desert 
farther north. Its appearance is somewhat suggestive of al- 
tered rhyolytes of Carboniferous and Triassic series in north- 
ern California, but I would rather connect it tentatively witli 
the Cambrian series close by on the south; it has been meta- 
morphosed to the same extent. 
THE SCHISTS IN CAJON PASS. 
About two miles south from Cajon station, the railroad 
enters a gorge which Cajon creek has cut through mica 
schists. They strike northwest-southeast and dip northeast at 
a high angle. The first member encountered is a gray, rather 
coarse granular mica schist resembling the Pelona series and 
also certain phases of the Abrams mica schist. Next come 
some green schists which appear like sheared greenstone and 
may be a metamorphosed diabase dike. Some granite also 
appears. Then follows a great bed, very thick, of a light gray, 
very fine grained rock which seems to be a fine micaceous 
quartzyte schist. The railroad is on this formation for several 
miles, to and beyond Keenbrook staffon. It is a different schist 
than any ever before observed by me in California and I am 
unable to suggest an age for it. It seems to pass under the 
ordinary mica schist, some of which, however, is interstratified 
with it. 
