32 GEOLOGY — CANOE CREEK. 



forming a nearly level lava plain, a kind of congealed sea, of which the surface was everywhere 

 roughened by 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 "manzanita." 



At numerous points on this lava plain we passed miniature volcanic vents or chimneys, which 

 had evidently been formed by 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 fall examination of 

 their internal structure. They seemed to be conduits through which streams of lava had con- 

 tinued to flow when surrounded by a congealed and solid crust. They may in some cases have 

 been modified by currents of water running through them, but it seems impossible that their 

 origin could be 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 bounding 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. Near 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. 



TRAP PLATEAUS BORDERING CANOE CREEK. 



Infusorial marls. — The banks 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 tra >. They are, perhaps, best exposed in the canon formed 

 by the passage of the river through "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 be said to form more than two distinct beds. Of these, the upper is white and fine as 



