70 Canadian Record of Science. 
in depth, situated on the top of the plateau. It was excavated, as 
its name indicates, by the drainage system of the Little Colorade 
River—the Colorado Chiquito of the Mexicans—and consequently 
is lowest at the north, its slope being away from the southern edge 
of the plateau. The river has cut its bed down to about 820 meters 
(2,700 feet) at the point where it empties into the Grand Cajon of 
the Colorado, and throughout the lower part of its course it flows 
through a cation considerably below the level of the desert proper, 
the lowest part of which is but little less than 1,200 meters (ap- 
proximately 4,000 feet) in altitude. Its upper limit may be set at 
1,800 meters (6,000 feet). The term Painted Desert should be 
restricted, it seems to me, to that part of the basin which is below 
1,500 metres (approximately 5,000 feet). 
The geology of the region is simple. The lowest stratum which 
comes to the surface is carboniferous limestone; above this is red 
sandstone, which in turn is overlaid by the so-called variegated 
marls or argillaceous clays, sometimes capped by a thin layer of 
impure coal or lignite. The limestone appears on the west side of 
the river only (?), where it is soon buried under the ancient lava 
floods from San Francisco Mountain and neighboring craters. The 
red sandstone is encountered everywhere, sometimes as surface 
rock, sometimes as high cliffs forming the escarpments of broad 
mesas, and sometimes as curiously sculptured tablets standing on 
the plain. The marls are widely distributed, and in many places, 
particularly south of the lower part of Moencopie Wash,? rise from 
the surface levelin the form of strangely eroded hills and ranges of 
stratified cliffs, whose odd shapes and remarkable combinations of 
colors—red, white, blue, brown, yellow, purple and green—have 
given the area in which they occur the name “ Painted Desert.” 
There are hundreds of smoothly rounded, dome-shaped hills of 
bluish clay, utterly devoid of vegetation, and almost identical in 
appearance with the “gumbo hills,’ of the Bad Lands bordering 
the Little Missouri in North Dakota. Both the hills and the naked 
clayey flats between them abound in alkali vents—miniature cra- 
terlets—where the alkali effloresces, crusting over the surface in 
patches which resemble newly fallen snow. Many of the hills are 
capped with fossil wood, and many of the flats and lower levels 
east of the Little Colorado River are strewn with chips and pieces 
which have tumbled down during the wearing away of the hill- 
sides. Logs 30 to 50 centimeters (roughly, a foot or a foot anda 
half) in diameter and 9 to 12 meters (30 or 40 feet) in length are 
1 The area below 1,370 meters (4,500 feet) is about 120 kilometers (75 miles) in 
length, and that below 1,500 meters (5,000 feet), 200 kilometers (125 miles). ‘The 
long axis of the desert, slightly crescentic in form, and curving from near the 
mouth of the Little Colorado in the northwest to New Mexico in the southeast, 
is 520 kilometers (200 miles) in length, with a transverse diameter of about 110 
kilometers (70 miles) along the middle portion, and a total area of ~9,800 square 
kilometers (11,500 square miles). Its eastern edge penetrates the boundary of 
New Mexico in two arms, following the usually dry courses of the Zuni and 
the Carrizo, and nearly reaches the boundary along the Rio Puerco, the largest 
tributary of the Colorado Chiquito. 
2 The terms “ wash” and “ arroyo > are applied to the deep channels or ravines 
so common in arid regions. ‘‘‘These arroyos are natural consequences of the 
unequal manner in which the rain falls throughout the year. Sometimes not a 
drop falls for several months ; again, it pours down ju a perfect deluge, washing 
deep beds in the unresisting soil, leaving behind the appearance ot the deserted 
bed of a great river.’—Emory, Mexican Boundary Survey, I, 1857, p. 57. 
