286 GEOLOGY OF THE HIGH PLATEAUS 



snows. Early in autumn the snows have disappeared and the lakes cease 

 to outflow, but never dry up. 



The length of the Aquarius from northeast to southwest is about 35 

 miles, and its breadth from 10 to 18 miles. Its altitude varies from 

 10,500 to 11, GOO feet above sea-level. Over three-fourths of its periphery 

 is bounded by massive cliffs, while along the remaining fourth it declines 

 gently to its confluence with the Awapa. Its upper portion is a lava-cap 

 of vast dimensions, varying from 1,000 to 2,000 feet in thickness. Its lavas 

 are seen in greatest mass at the northwestern flank, overlooking the south- 

 ern part of Grass Valley and the Panquitch Hayfield. Upon the southern 

 and eastern sides, at the foot of the volcanic wall, the long slopes begin, 

 which reach far out into the mesas of the inner Plateau Country. Their 

 descent is slow and easy to all appearance, but they are deeply gashed with 

 profound canons and terrible gorges, among which it is dangerous to ven- 

 ture. To traverse these slopes it is necessary to keep high up near the base 

 of the lava-cap, where the ravines head, and where they are sufficiently 

 open to afford a practicable trail. Even here the journey around the base 

 of the cliff is laborious, involving the constant ascent and descent of vast 

 gorges and amphitheaters, and requiring many days to accomplish it. Yet 

 the traveler who has abundant strength and perseverance will be amply 

 rewarded, provided he has chosen his way with prudence and good judg- 

 ment. Upon these slopes the structure of the plateau is revealed. 



In truth, there is but little "structure." The plateau is simply a rem- 

 nant left b)'" the erosion of the country around its southern and eastern 

 flanks. A few of its minor features are due to displacements, and its west- 

 ern wall originated in a great fault or rather in several faults. The rest of 

 the mass owes its pre-eminence to circumdenudation. We may gain some 

 notion of the stupendous work which has accomplished this result by taking 

 our position upon the southeastern salient at the verge of the upper platform. 



It is a sublime panorama. The heart of the inner Plateau Country is 

 spread out before us in a bird's-eye view. It is a maze of cliffs and ter- 

 races lined off with stratification, of crumbling buttes, red and white domes, 

 rock platforms gashed with profound canons, burning plains barren even of 

 sage — all glowing with bright color and flooded with blazing sunlight. 



