North of the Grand Cation of the Colorado. 457 
tom of the Grand Cafion north to the plateaus in which the 
streams mentioned have their sources, we pass over the up- 
turned edges of nearly 25,000 feet of geological formations. 
Commencing below, in the most southern bends of the Grand 
Cafion, we find about 1,000 feet of metamorphic crystalline 
schists, with dykes and beds of granite. In the lateral cafions, 
which enter from the north, we discover another group of rocks, 
Sive erosion intervening. The rocks are of Pre-carboniferous 
age. No fossils have been found in them, but the Carboniferous 
rocks lie on their upturned edges, so that there was a long 
period of erosion separating these formations also. The Car- 
boniferous sandstones, limestones, and shales, next succeeding, 
are from 4,000 to 5,000 feet in thickness; then we have about 
2,500 feet of what are deemed to be Triassic rocks; next we 
have 1,000 or 1,200 feet of Jurassic rocks ; still surmounting 
these, we have 1,800 or 2,000 feet of Cretaceous beds, and then 
we reach Tertiary rocks, 3,000 or 4,000 feet in thickness in this 
district, but farther to the north obtaining a thickness of nearly 
, et. 
The most remarkable features of the country are the deep 
narrow cafions by which it is interrupted, making its explora- 
reach a line of cliffs from 100 to 400 = in pre 
escarpment is ca) by a firmly cemented conglomerate con- 
taining man ee silicified wood, and over its surface 
are scattered many like fragments, and sometimes huge tree- 
trunks, which are the remnants of rocks at one time overlying 
