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QUATERNARY CONGLOMERATES—SPIRE RANGE. 23 
A portion of the Tertiary series which underlies most of the Colorada basin closely resembles 
this deposit, being composed of similar materials dovbtless.accumulated under the same phys- 
ical conditions. But in most of the exposures of the Tertiary conglomerates they are much 
more metamorphosed and consolidated than those under consideration, and are associated with 
infusorial strata, which are here wanting. I have been disposed to regard the stratified gravels 
exposed at Conglomerate Bluffs, as well as those which underlie the desert surfaces of all the 
subordinate basins traversed by the Colorado, as accumulations of materials transported by its 
waters, or derived from the adjacent mountains, and stratified in the bottoms of these basins 
when occupied by bodies of water. The Colorado having since greatly deepened its channel, 
the materials formerly deposited by it are now left standing in high bluffs on either side of its 
course. ; 
A few miles above Conglomerate Bluffs, (Camp 17,) a high crag overhangs the water on the 
east side of the river, composed of stratified conglomerate, similar, in general character, to 
that of the bluffs, but metamorphosed, greenish in color and highly inclined. This conglome- 
rate is overlaid by a thick bed of purplish trachyte, which has apparently been the agent of 
its metamorphosis. 
Fig. 2.—spmre RANGE. 
This bed of conglomerate I was at first disposed to regard as identical with that forming the 
bluffs below, but subsequent observation led me to consider it the equivalent of the metamor- 
phosed conglomerates exposed at various points higher up the river, which are older than the 
quaternary, being probably the representatives of a portion of the miocene series of the Cali- 
fornian coast, 
We here obtained a fine view of a remarkably picturesque chain of mountains on the west 
side of the river, stretching away toward the northwest. . It is crowned by a range of pinnacles, 
not unlike Chimney Peak in form and apparently composed of similar material, which suggested 
the name given it of Spire range. This chain bears an intimate relationship in its geological 
