H. J. Biddle — Surface Geology of Southern Oregon. 479 



rounded and subangular pebbles, though in places these occur 

 but sparingly. In the northernmost part of the ancient lake 

 basin is a row of round topped hills, stretching five or six 

 miles from the mountain border on the west and nearly span- 

 ning the valley. These hills rise fully 200 feet above the level 

 plain at their feet, and are covered from base to summit with 

 water- worn gravel. While it is evident that these vast accu- 

 mulations of gravel were formed by the waves and currents of 

 the ancient lake, yet it is not clear to the writer how they ob- 

 tained their present form. The supposition that an ancient, 

 and once continuous, gravel bar or embankment has been cut 

 to its base,- at several points, by lines of recent drainage, par- 

 tially explains the peculiar topography. 



Passing to the extreme northern end of the valley, the pass 

 leading to Abert Lake is found to be lower than the ancient 

 beach lines and gravel accumulations alluded to. At the divide 

 in this pass, and thirty or forty feet above the lowest point, a 

 considerable quantity of water-worn pebbles may be seen on 

 the hillside. Taking these facts into consideration, it is irn^ 

 possible to avoid the conclusion that when Goose Lake Yalley 

 was filled to its highest beach line its waters overflowed this 

 pass, and communicated with the lake north of it. But the 

 ancient shore lines cannot be traced from one valley to the 

 other, owing chiefly to the broken nature of the country ; and 

 the evidence of this fact is not as clear as could be wished. 

 When the pass alluded to was overflowed it must have formed 

 a narrow strait, of no great depth, connecting two large bodies 

 of water. Goose Lake found an outlet at its southern end, 

 and hence this strait might have furnished an outlet to the 

 ancient lake north of it, by which it could discharge its sur- 

 plus water. This question will be referred to later on. 



Although Goose Lake does not at present overflow, yet a 

 rise of but a few feet would cause its waters to discharge south- 

 ward into the North Fork of Pit River, and thence into the 

 Sacramento. This is reported by Russell* to have taken place 

 as recently as 1860, and again for a short period in 1881. 

 When the lake stood at the level of its highest beach line, it is 

 evident that the valley of Pit River was yet to be cut ; and the 

 depth to which the waves eroded the mountain side shows that 

 . for a long time the lake maintained a nearly constant level, 

 and nothing was accomplished toward deepening the channel 

 of discharge. But when the cutting down of this channel com- 

 menced it must have been comparatively quickly accomplished, 

 as is shown by the absence of beach lines at lower levels than 

 those mentioned. Perhaps other lakes, on the lower courses of 

 Pit River, had first to be drained ; and not until this had been 



* Reconnaissance in Southern Oregon, p. 456. 



