GEOLOGICAL SUKVEY OF THE TERRITORIES. 666 



Euby City. They consist of bones of the mastodon, rhinoceros, horse, 

 elk, and other large mammals, of which the species are probably in some 

 cases new, in others identical with those obtained from the fresh-water 

 tertiaries of the " bad lands" by Dr. Haydeu. With these mammalian 

 remains are a few bones of birds and great numbers of the bones and 

 teeth of fishes. These last are cyprinoids allied to Mylopharodon, Milo- 

 cheilus, &c, and some of the species attained a length of three feet or 

 more. There are also in this collection large numbers of fresh- water 

 shells of the genera Unio, Corbicula, Melania, and Planorbis. All these 

 fossils show that at one period in the history of our continent, and that, 

 geologically speaking, quite recent, the region under consideration was 

 thickly s,et with lakes, some of which were of larger size and greater 

 depth than the great fresh- water lakes which now lie upon our northern 

 frontier. Between these lakes were areas of dry land covered with a 

 luxuriant and beautiful vegetation, and inhabited by herds of elephants 

 and other great mammals, such as could only inhabit a well-watered 

 and fertile country. In the streams flowing into these lakes, and in the 

 lakes themselves, were great numbers of fishes and mollusks of species 

 which, like the others I have enumerated, have now disappeared. At 

 that time, as now, the great lakes formed evaporating surfaces, which 

 produced showers that vivified all their shores. Every year, however, 

 saw something removed from the barriers over which their surplus water 

 flowed to the sea, and, in the lapse of time, they were drained to the 

 dregs. In the Klamath Lakes, and in San Francisco, San Pablo, and 

 Suisun Bays, we have the last remnants of these great bodies of water; 

 while the drainage, of the Columbia lakes has been so complete that in 

 some instances the streams which traverse their old basins have cut two 

 thousand feet into the sediments which accumulated beneath their 

 waters. 



The history of this old lake country, as it is recorded in the alterna- 

 tions of strata which accumulated at the bottoms of its water basins, will 

 be found to be full of interest. For while these strata furnish evidence 

 that there were long intervals when peace and quiet prevailed over this 

 region, and animal and vegetable life flourished as they now do nowhere 

 on the continent, they also prove that this quiet was at times disturbed 

 by the most violent volcanic eruptions, from a number of distinct centers 

 of action, but especially from the great craters which crowned the sum- 

 mit of the Sierra Nevada. From these came showers of ashes which 

 must have covered the land and filled the water so as to destroy immense 

 numbers of the inhabitants of both. These ashes formed strata which 

 were, in some instances, ten or twenty feet in thickness. At other times 

 the volcanic action was still more intense, and floods of lava were poured 

 out, which formed continuous sheets hundreds of miles in extent, pene- 

 trating far into the lake basins, and giving to their bottoms floors of 

 solid basalt. When these cataclysms had passed, quiet was again re- 

 stored, forests again covered the land, herds dotted its pastures, fishes 

 peopled the waters, and fine sediments abounding in forms of life accu- 

 mulated in new sheets above the strata of cooled lava. The banks of 

 the Des Chutes Biver and Columbia afford splendid sections of these 

 lake deposits, where the history I have so hastily sketched may be read 

 as from an open book. 



But it will be said that there are portions of the great central plateau 

 which have not been drained in the manner I have described. For here 

 are basins which have no outlets, and which still hold sheets of water of 

 greater or less area, such as those of Pyramid Lake, Salt Lake, &c. The 

 history of these basins is very different from that of those already 



