364 C. R, KEYES^ OROGRAPHIC ORIGIN OF LAKE RONXEVILLE 



toil places i)avticular emphasis on the rapidity of the hitest uprising of 

 the dome;, and Later o1:)servers fully snl)stantiate him. 



HIGH CHANNEL OF YIRGKN-MUDDY FIVER 



The elevation of the hottom of the canyon occupied hy Muddy Creek 

 nenrly 1,500 feet ahove the water level of the Colorado Eiver proclaims 

 tlie speed with which the Colorado dome has recently revived its upward 

 movement. IMuddy Canyon was excavated manifestly hy a very much 

 larger stream tlian the one now occupying it. This feature apj^ears to 

 also characterize other tributaries of the Colorado Eiver. In view of tlie 

 fact that a generation ago the glacial activities were so widely evoked to 

 explain everything geological, it is not so very strange that Dutton 

 should also ascribe this peculiarity to conditions of moister climate when 

 tlie present diminutive and often intermittent creeks were hypothetically 

 considerable rivers. TJiat some of these rivers might have, been deprived 

 of their waters ])y the effects of tlie uprising movement itself without 

 notable change in the local climate does not seem to have occurred to 

 him. Under these circumstances, it is quite remarkable that any traces 

 of the ancient drainage system should survive the vicissitudes of moun- 

 tain-forming, lake, and desert wind activities. This is especially true 

 since the latter have come to be better understood and their tremendous 

 potency recognized. There would now remain no wind-ga]3 at the south- 

 ern end of the old valley. The canyon of the one-time stream draining 

 tlie basin in the pre-lacusti'ine epoch might lie presei'ved beyond the line of 

 the orographic barrier; but wind erosion and eolic deposition would soon 

 obliterate all traces of the old channel at and on the flanks of the barrier. 



The pertinent cpiestions which now arise are whether or not the present 

 size of the Virgen-J\luddy Canyon is commensurate with the probable 

 volume of the old stream, and whether it was jiossible for such a stream 

 once to have crossed the line of the orograjihic barrier? To both of these 

 cpiestions the answer is strongly affirmative. 



DIVER^^ION OF HEAhWATFh'H OF 0]J) VrROEN RIVER 



Every explanation of the genesis of Lake Bonneville necessarily postu- 

 lates a much larger supply of water than that at jiresent afforded to Great 

 Salt Lake. In accordance with the ])revailing hy])()thesis, this surplus 

 volume of water was secured through means of moister climatic condi- 

 tions that were sui)erinduced by the Ghicial epoch. With the joassing 

 away of the latter, according to the same notion, the great expanse of 

 waters rapidly diminished. 



Ordinary lakes have tlieir size and heiglit of surface controlled by their 



