The basalt plateau of eastern Washington exhibits a peculiar assemblage of physiographic features, including a complex set of interlocking stream channels, abandoned canyons and cataracts, steep-walled buttes, rock-rimmed basins, residual islands of loess between the channels, bar-like deposits of rubbly gravel, and slack-water deposits in certain tributary valleys, which have been described at length by Bretz.2 He has attributed these features to a catastrophic flood of glacial waters, diverted southwestward across the plateau by a glacial dam in the Columbia River valley on the north edge of the plateau. According to Bretz, these waters were released suddenly and in such volume as to occupy all the channels simultaneously and even to spill across divides into neighboring discharge ways. The torrent of glacial waters thus conceived, Bretz called the Spokane Flood. Critical examination of the area by the writer has revealed new facts regarding the extent of the flood between . . .