32 
GEOLOGY-CANOE CREEK. 
forming a nearly level lava plain, a kind of congealed sea, of which the surface was everywhere 
roughened hy waves cooled while flowing; their crest black and ragged; the troughs containing 
a little ash-like soil, which supported a tangled growth of “ sage” and “mansanita.” 
At numerous points on this lava plain we passed miniature volcanic vents or chimneys, which 
had evidently been formed hy the bursting out of steam or gases from below, and in more than 
one instance we noticed subterranean galleries, or caverns, having a diameter of fifteen to twenty 
feet, an irregularly circular section, and extending indefinitely in either direction. 
In some places the roofs of these passages had fallen in, permitting a full examination of 
their internal structure. They seemed to he conduits through which streams of lava had con¬ 
tinued to flow when surrounded hy a congealed and solid crust. They may in some cases have 
been modified hy currents of water running through them, hut it seems impossible that their 
origin could he due to the action of any such agent. 
Similar galleries have been described by Prof. Dana and Dr. Winslow as occurring on the 
lava plains of the Sandwich Islands, and they seem to be a constant feature in the phenomena 
of great overflows of lava. 
The chimneys to which I have referred probably communicated with these passages. 
An oasis in this barren waste was formed by a stream of pure cold water, which issued from 
the cavernous wall hounding this plain on the east, ran half a mile, in many winding, life-giving 
channels, then fell into a chasm and disappeared. 
The geology of the region bordering Canoe creek throughout its course is exceedingly mono¬ 
tonous. Cliffs, ridges, or tables of dark scoriaceous trap border it on either side, from the 
crossing of the emigrant trail to its mouth. Hear its junction with Pit river, the tables of trap 
occurring on its banks exhibit a remarkable symmetry. They form a series of nearly level plateaus 
gradually rising in successive grades and receding from the stream. They terminate towards 
Canoe creek in abrupt, frequently mural edges, and present the same arrangement on both sides 
of it, as represented in the figure. 
Infusorial marls .—The hanks of Pit river, both above and below the mouth of Canoe creek, 
are partially formed of regularly stratified sedimentary deposits ; the first seen since leaving 
the valley of the Sacramento. 
They appear on both sides of Pit river at intervals for several miles, being in many places 
interrupted or covered by beds of trap. They are, perhaps, best exposed in the canon formed 
hy the passage of the river through £i Stoneman’s ridge,” the most conspicuous of the lines 
of upheaval, which form what is known as the lower canon of Pit river. 
They here exhibit a thickness of about fifty feet, but are considerably tilted up, and are 
covered by a thick bed of trap, which has been poured out over them. 
They exhibit narrow and parallel lines of deposition, but are very homogeneous, and can 
hardly he said to form more than two distinct beds. Of these, the upper is white and fine as 
