TUIO GllAND CA5fON DISTIUGT. 
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strata. The summits of the terraces dip to the northward, while the streams 
run southward. They thus form each a chain of canons. Thus, Kauab 
Creek, with its upper tributaries flowing in open valleys, at length begins to 
cut into the Jurassic, and its gorge, ever deepening, at length becomes 
nearly a thousand feet in depth. Suddenly the canon walls swing to rtght 
and left to form the mural front which terminates the Jurassic terrace, and 
the river, now at the summit of the Trias, is once more in open country ; 
but only for a short distance, for it soon begins to cut into the Trias, form- 
ing a great canon as before. The same process is repeated and the river 
flows out of its Triassic chasm into the open again, while its walls swing in 
either direction to form the terminal escarpment of the Triassic terrace. 
The three streams just mentioned are not the only drainage channels 
in the terraces, though they are the principal ones, and sooner or later 
gather the greater part of the drainage. There are many canons in the ter- 
races, and they all have the same relation to the clilFs and to the dips of the 
strata. They cut into the terraces and emerge from them at the bases of 
their several cliffs. All except the three first mentioned are dry, carrying 
iro streams except spasmodic floods dm-ing heavy rains and the melting of 
the snows. Many of them are actually filling up, the floods being unable 
to carry away all the sand and clay which the infrequent rains wash into 
them. 
