116 THE CANADIAN NATrRALIST. [Vol. Vl. 



period in the IJstory of our continent, and that geologically 

 speaking quite recent, the region under consideration was thickly 

 set 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 ujamn:als, such as could 

 Only inhabit a well-watered and fertile country. In the streams 

 flowing into these lake.s, and in the lakes themselves, were great 

 numbers of fishes and molusks, of species, which like the others I 

 have enumerated, have now dissappeared. At that time, as now, 

 the gro.it 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, thej' 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 wat-^r; 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. 



Tie history of this old lake country, as it is recorded in the 

 alternations of strata which accumulated at the bottoms of its water 

 basins will be found full of interest. For while these strata 

 ^urnish evidence that there were long intervals when peace and 

 quiet prevailed over this region, and animal and vegetable lifo 

 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 centres or action, 

 but especially from the great craters which crowned the summit 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, penetrating far into the lake basins, and giving 

 to their bottoms floors of solid basalt. When these cataclysms 

 had passad, quiet was again restored, forests again covered the 

 lanJ, herds dotted its pastures, fishes peopled the waters, and fine 

 sediuieiitj, abounding in forms of life, accumulated in new sheets 



