‘Mesozoic and Cenozoic Geology and Paleontology. 95 
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the usual lake terraces, of which there are two well-defined lines at 
least, and the river terraces, which are confined to the streams, and do 
not seem to have any direct connection with the former. The lowest 
plain valley opposite the canon, near the water’s edge, is 4,344 feet 
above sea level; 1st terrace, 4,683 feet; 2d terrace, 4,776 feet; and 3d 
terrace, 3,858 feet. These terraces show the gradual decrease, step by 
step, of the waters of the ancient lake, and the operations of the little 
streams pouring into it from the mountains on either side. The 
amount of local drift that has been swept down through the gorges or 
canons and lodged at the opening is very great. At the immediate 
mouth of the canon, the bowlders are quite large, varying in diameter 
from a few inches to several feet. Westward toward the shore of the 
lake the bowlders diminish in size and quantity, and the finer sedi- 
ments, as sands and marls, increase, showing a constant decrease in 
the power of the currents of the water after leaving the mouth of the 
canon. 
The local drift is conspicuous in Logan Canon. It is composed of 
rounded bowlders, with clays and marls, reaching a thickness of 100 to 
150 feet in regular and horizontal strata, attached to the sides of the 
gorge, and showing that, however turbulent the waters, the materials 
were deposited in a lake, At the entrance of the canon are some re- 
markable terraces, composed of sands, clays, marls and rounded 
bowlders. 
A large portion of Utah is made up of nearly parallel ranges of 
mountains, trending nearly north and south, with intervening valleys 
of greater or less width, which, after their elevation, formed shore lines 
for detached lakes or bays. It would appear that the last lake-period 
of this portion of the west commenced in the Pliocene epoch, and con- 
tinued on up to the present time; that the waters once filled all these 
valleys, so that they rested high upon the sides of the mountains, de- 
positing what Prof. Hayden called the Salt Lake Group, gradually 
passing into the Post-pliocene deposits which verge upon our present 
period. It is quite possible that there have been oscillations of leve] 
in these modern lake-waters; but so far as the proofs go, this great in- 
land lake may have continued quite uniform until the terrace epoch, 
and that then the waters gradually receded to their present position. 
The immediate valley of Bear river, near the crossing, is interesting 
on account of the fine development of the lake-deposit, which is com- 
posed of clay, sand, and marl, yellow and rusty-drab color, and attains 
. a thickness of 200 to 300 feet. The elevation of Bear river valley, at 
