AN OBSIDIAN IMPLEMENT FROM PLEISTOCENE DEPOSITS IN NEVADA
Walker river has the form of a compressed horseshoe. It gathers among the foothills of the Sierra Nevada mountains in Eastern California, between the fair Lake Tahoe-the gem of the Sierrasand the foul Lake Mono, and, quickly embouching from the narrow canons of its birth into the broad valley of its principal course, passes into Nevada between the Sierras and the Wassuck mountains (or Walker River range). Thence for 50 miles northward it meanders though the flat-bottomed Walker valley in a
... er valley in a shallow willow-fringed channel. Opposite the north end of the Wassuck mountains its course swerves to the eastward and then to the southward through a contracted valley or outer cafion sweeping around the end of the range; and the southerly course is maintained 20 miles before the river falls into the lake of the same name in which its waters extend yet another 20 miles southward. At the toe of the horseshoe, around the northern extremity of the enclosed mountain range, the previously shallow channel deepens, and the river flows through a steepwalled inner cafion, reaching 300 feet in depth ; and in the cafion walls the deposits of the valley are exposed in a superb series of stratified beds from which the Pleistocene history of the region may be easily read. The valley of Walker river, from a few miles below the embouchure of its mountain-bound cafions to and beyond the extremity of the lake in which its waters are evaporated, forms a part of the basin of the extinct Lake Lahontan, which has been restored and immortalized by King and Russell; and the history recorded in these deposits coincides with that read from the mechanical sediments, the chemic precipitates, and the ancient shore lines of other parts of the same old lake and of other extinct lakes in the same quarter of the country. This history comprises three principal episodes : E i q an episode of cold and wet, during which glaciers formed within the mountains, and outletless lakes formed or expanded in the valleys ; 302 THE AMELUCAN ANTHROPOLOGIST. [Vol. 11. second, an episode of warm and dry climate, during which the glaciers melted, the lakes were evaporated to or below their present level, and caiions were cut in the newly formed sediments ; thi~d, a shorter episode of cold and wet, during which glaciers again formed in the mountains, and lakes in the valleys, and another sheet of sediments was laid down ; and then came the present period of d r y and warm climate, during which the glaciers were obliterated and the lakes evaporated, and the sediments, new and old alike, were laid open by the rivers in their descent toward the lowest points in the mountain-bound basins. Some of the details of the general history are obscure, but they are elucidated in a measure by the present condition of the region. In the present episode of warm and dry climate, the Lake Lahontan area is a sun-scorched semi-desert, with scant foliage on the mountains, with the meagre and sickly verdure of desert plains (save where reclaimed by irrigation) in the valleys, with rare springs on the slopes, and with shrunken lakes of bitter water in the lowest depressions; the fauna is still poorer in species and generally in individuals than the poor flora; and the human population found by the white pioneers--the " Diggers" of the early overland pilgrimswas perhaps the most wretched and degraded of the land. The present conditions of aridity in climate and poverty in life must reflect and repeat the like conditions of the inter-lacustral period. With the second chilling of climate and checking of evaporation, the rivers and lakes expanded, a richer and more varied fauna immigrated or developed, and the elephant and rhinoceros, the camel and horse, the ox and the deer left their bones by thousands in the marshes about the shores of the sweetened lakes; moreover, to support a fauna so rich and varied, an equally rich and varied flora must have covered the upper valleys and clothed the lower mountains. And this wealth of life manifestly reflected and repeated the like condition during the first episode of cold and wet. So the Walker river deposits and their correlatives, and the present condition of the region, together record two epochs of meagre life, one of which is past while the other persists, and two epochs of abundant life, both long past ; and the latter have been demonstrated by physical geologists to correspond with the two great ice invasions of the northeast. On October 6th, 1882, I rode along the low scarps and higher salients of white marl forming the walls of the inner cafion of oct. 1889.1 AN OBSIDIAX IMPLEMENT.