GEOLOGY. The southern half of the Wash ington Cascades, and the whole of eastern Wash ington south of the Great Bend and the Spokane River, are covered by an immense sheet of basalt forming part of the great Oregon lava-tlow, the most extensive volcanic outburst known on the globe. It is of geologically recent origin—Noma Rainier still give,; evidences of volcanic activity —and over large areas it has been but little dis turbed or eroded. The rivers, however, have eta deep canons through it. which in the case of the Snake River penetrate into the underlying rocks, showing the lava field to he 1000 and 2000 feet in thiekness. about 100 miles around the continence of the Snake and Columbia riv ers the lava is overlaid by an irregular deposit of unconsolidated sand. Clay, and voleanie dust dating front late Tertiary tunes and known as the John Day formation, having been laid down in the ancient Lake .101111 Day. The
northern half of the Cascades and the country of northeastern Washington consist mainly of ancient crystalline rocks and Lower Paleozoie strata. In West ern \Washington Cretaceous and Tertiary deposits are the prin cipal surface formations, though Carboniferous strata are upturned around the volcanic centre of 'Mount Olympus. The northern part of the State was covered by the Pleistocene ice-sheet, which left a heavy drift covering around Puget Sound, and is supposed to have formed the channels of the latter by its scouring action. It also dammed the Columbiat River at the Great Bend, and forced it into a nett• and more southerly channel now indicated by the remark able 'Grand Coul6e.' When the ice retreated the river resumed its old channel.