EASTERN SLOPE OF THE CORDILLERAS. 99 



Blate in the San Gorgoiio pass. About four miles below the summit, on each side of the pass, 

 are high hills, with sharp outlines and ragged crests of crystalline felspar, intersected by 

 quartz veins of a brownish red color, and hardly deserving the name of granite. These oc- 

 curring on both sides of the pass must also cross it and produce a second axis eastward of the one 

 lower down. To this axis may be attributed the dislocation and tilting of the pink strata, and 

 in this axis the crystalline limestone may belong. 



In ascending the last five miles of the pass, and especially the last three, thick beds of con- 

 glomerate and sandstone appear, which form the bluifs referred to. Sections afforded by the 

 creek often exhibit 100 feet of thickness, and as all the beds were not exposed at one place, I 

 think 300 feet to be the approximate thickness of these conglomerates in this place. From the 

 lines of deposition they appear to be horizontal ; but viewing the slope to the Great Basin 

 as merely the upper surface of tbese strata, the true dip may be about 6° northeast. They are 

 yellow colored and very friable, being in some beds wholly unconsolidated. They contain 

 angular felspathic crystals and paste similar to the pink beds alluded to, with the addition of 

 gneiss, mica slate, and quartz pebbles, both rounded and square fragments of all being freely 

 mingled in the mass. This addition serves in part to distinguish these conglomerate beds from 

 the pink sandstones. They are still further recognized by their want of consolidation, and by 

 their unconformability to the strata on which they rest. The pink sandstones repose on the 

 axis, have been upraised and contorted by the elevating force, while, on the contrary, the upper 

 conglomerates are almost horizontal, and are undisturbed by any cause. Derived in a great 

 degree from the same sources, (primary granitoid rocks,) they mark successive periods of 

 deposition. 



The descent from the summit of the Cajon pass to the Mojave river, where the trail strikes it, 

 is over the back of the pink sandstones referred to in the description of the pass, and capped by 

 the conglomerates. The slope of the surface of the strata towards the river is 20°, a slope 

 greater than that of the beds themselves, inasmuch as the inferior fourth of the slope is very 

 much worn into ravines and canons by the water draining from off so large a level surface 

 higher up. The true dip of the strata is northeast. The soil on this slope is a mixture of 

 quartz and felspar, granitic detritus in fine powder, with pebbles of quartz, gneiss, and mica 

 slate, derived from the degradation of the conglomerates. 



The tree yucca, of every possible form and size, was the predominant vegetation. Cedar 

 trees of small size in the valleys near the summit, immediately below the pass. Dwarf pine, 

 chemisalj and artemisia were the other shrub growths. The herbaceous vegetation was similar 

 to that of the San Gabriel and Los Angeles valley ; but the individuals on a dwarf scale. The 

 whole vegetable growth is that of a desert region, and contrasts wonderfully with the luxuriance 

 on the west side of the mountain range, the difference being due to the deficient supply of water 

 on the east side of the Cordilleras. 



The rains falling upon the eastern summits of the sandstone strata and the melting of the 

 winter snows form a body of water which sinks between the laminaj and finds a subterranean 

 course toward the valley of the Blojave, where, by their oozing out from the worn edges of the 

 strata, they form springs, and go to swell the volume of the river itself. 



The Mojave river, where first struck, has a course north by west — lies several feet below the 

 level of the sandstone in a small channel about thirty yards wide, worn in the strata ; by cut- 

 ting its way across the dip of the sandstones, and to some depth downwards, it has tapped some 

 of the subterranean water courses alluded to. Along the whole course of the river it is very 



