DEVELOPMENT OE CLIFF PROFILES. 
257 
everywhere, in fact, throughout the Kaibab division the platform of the 
Middle Ten-ace is obliterated and the entire Carboniferous series forms one 
wall of alternate vertical ledges and taluses. The reason for this difference 
will soon become manifest. 
Let us now pursue further the evolution of the cliffs by imagining the 
sinking of a stream by corrasion into the Red Wall series. This forma- 
tion, constituting the lower Carboniferous of the southwestern Plateau 
Country, is one of the most extraordinary in the world. It is composed 
principally of limestones of the most massive and homogeneous description, 
one bed being over 750 feet in thickness without any visible horizontal part- 
ing ; another of nearly 400 feet, and a third of more than 300 feet. There are 
also several other massive layers of limestone, and these calcareous beds are 
quite similar to each other in their lithological characters. At the summit 
of the Red Wall is a group of calcareous sandstones, very heavily bedded 
for the most part, and about 350 feet in total thickness. Beneath the huge 
limestone members other calcareous sandstones appear in considerable mass, 
with a thickness of about 750 feet. These lower beds are conspicuous to 
the eye by their deep rich brown color. With the exception of the largest 
limestone member, all of these great beds vary somewhat as they pass 
through great horizontal distances. They often subdivide into thinner beds 
and the amount of arenaceous matter which they contain also changes. 
These changes of character, however, are seldom or never abrupt, but 
usually take place by almost imperceptible degrees along many miles of ex- 
posure. In the Kanab division the whole series of nearly 2,500 feet thick- 
ness is wonderfully massive, and the partings of the strata are comparatively 
few. In the Kaibab the great 750-foot limestone is as solid as ever, but 
most of the other members have become laminated much more minutely 
than in the Kanab and Uinkaret, and are of more perishable texture. The 
results of the attack of weathering upon the edges exposed by corrasion 
vary accordingly. In the Kaibab several causes have combined to produce 
a far greater amount of destruction in the Red Wall series than in the 
Kanab and Uinkaret divisions. 
The causes which have produced in the Kaibab a topography differing 
so widely from that which is seen in the other divisions of the chasm may be 
17 G 0 
