294 
April 23, 1897) and Emmons (ScrencE, July 
2d), as to the antecedent origin of the Green 
river in its passage through the Uinta moun- 
tains, I would suggest an independent and con- 
firmatory argument for the consequent origin 
of the Green-Colorado in its passage across the 
plateaus of the Grand Canyon region, where it 
has been regarded as antecedent by Powell and 
Dutton. My argument is based on the curva- 
ture of the river and especially on its meanders. 
The meanders are surprising in themselves 
from the steepness of the river and their deep 
incision; yet more surprising is the location of 
strong meander reaches just up stream from 
structural displacements. It is the latter rela- 
tion that I wish to point out. 
In general, a river meanders when its de- 
clivity is low. The Mississippi below Memphis 
falls less than five inches to the mile and has a 
typical meandering course (See Table of Mean- 
ders). Yet the Colorado, falling more than 
seven feet per mile in the Canyon region, has 
stretches of even greater sinuosity and the dis- 
tribution of these winding reaches suggests that 
the river is not antecedent, but dependent on 
the dislocations for its path. 
The following table shows the rate of meander 
for measured stretches of the river, the rate 
being expressed in miles of actual stream to 
100 miles along a mean course traced evenly 
through the meanders, without departing more 
than a mile from the water at any point. In 
the first column is the name given by Powell 
to the stretches of river, in the second the miles 
of mean course, in the third the actual course, 
while the fourth contains the rate of meander: 
Desolation and Gray Canyons— 
Uinta R. to Book Cliffs,. ... 76 113 149 
Gunnison’s Valley—to San Rafael R| 30 35 117 
Labyrinth Canyon—to GrandR. . 51 93 182 
Cataract Canyon —to WN 37937’, 
WIN eos oad 6 pen 6.0 oo 77 81 105 
Glen Canyon and aboye—to PariaR| 88 139 158 
Marble and Grand Canyons—to 
(Compal WEEINS Sb 505650500 2594 280 108 
Thence to California boundary... .| 139 145 104 
Mississippi— Memphis to Baton 
IMO a doo k oan soa yo 155 
SCIENCE. 
[N. 8. Vou. VI. No. 138. 
The 139 miles of strong meander above the 
Paria River bring the Colorado down to the 
East Kaibab monocline, where the course turns 
to the south to avoid the uplifted Kaibab pla- 
teau, just as the Green turns east on reaching 
the Uintas. This is best seen on the United 
States Relief Map, where the darker color is 
within the river’s elbow at the Uinta and 
against the Kaibab. 
At the monocline the river is deviated. In 
Glen Canyon above the monocline the me- 
andering is greater than the Mississippi’s. 
Below the meandering is reduced to a mini- 
mum. 
The conclusion is irresistible that the Kaibab 
uplift introduced a local baselevel (Powell’s 
phrase) that compelled the river to meander on 
a flat open course until the obstacle gave pas- 
sage to one side. 
Less than a hundred miles further north in 
the Cataract Canyon, near the junction of the 
Green and Grand, the river’s course is straight 
(meander rate, 105). Next above this is 
the very sinuous Labyrinth Canyon (rate, 
182). The geological map here shows a dome 
with Permian and Carboniferous brought to the 
surface, a part probably of the San Rafael dis- 
turbance. Through the dome the course is in 
the straight Cataract Canyon ; the Labyrinth 
Canyon is the northern approach. 
Is the analogy here to the Kaibab and Glen 
Canyon casual ? 
Gunnison’s valley is instructive. It has little 
meander and no uplift. Dutton reports it to 
be the only open valley on the river besides 
Brown’s Park, and attributes this character to 
the softness of strata that weather back too 
rapidly to stand in canyon walls. In this case 
surface meanders would be lost here, as the 
the valley would straighten as it widened under 
erosion. 
To the north the meandering is again great. 
At the time the river took to meandering it may 
well have had such a course from the Uintas to 
the dome, preserved to us where the rocks were 
hard and the river now runs in canyons, but 
lost in the softer strata. North of the Uintas I 
have no map, but this stretch of Gunnison’s 
suggests that meanders would not be preserved 
in the soft rocks of the Bad Lands. 
