gon. The valley of the Lower Columbia, in particular, reveals the immense overflows of lava in its forms of basaltic rock. In numerous places it occurs in solid masses of many feet in thickness ; in others it has assumed the columnar form ; and in many more it is broken into sharply angular fragments, mixed with earth. The fracture in the latter case is foliated,—every fresh cleavage showing what appears like the impression of palm- leaves. The most interesting form of basalt occurs in some columns in the high river-banks just below the town of St. Helen. These columns have been brought to view by the gradual process of denudation; and now project a dozen feet or so of their tops from the incline of the high bluffs. They consist of uniform blocks, of about ten inches in thickness, having six sides,—laid one above another so as to appear like a solid pillar. But their great peculiarity is that each individual block has a similar-sized chip off the lower side on its northwest corner or angle. With this exception the blocks are flat. Occasionally one gets thrown off, and so the columns never appear at any great height above the earth; but their fragments strew the river bank for a long distance.
This basaltic outflow evidently came from Mount St. Helen. On any of the sand-bars in the Lewis or the Cathlapootle River, which debouches into the Columbia on the opposite side, are to be found water-rolled fragments of pumice-stone in abundance ; and there are seasons of high water which bring down from Mount St. Helen by some of its streams—the Cowlitz in particular—so much white volcanic ash as to render the water milky in its appearance. It is somewhat remarkable that, while on the Oregon side the basalt covers every stratified rock or sedimentary deposit, on the Washington side the hills are immense deposits of coarse gravel or sand and water-rolled stones.
About in the central portion of the Wallamet Valley are some gravel-beds of no great thickness; while in Washington, along the Columbia and in the Puget Sound region, the soil is gravelly to an extent which renders it almost unfit for cultivation. Did the facilities which the sound offered for drainage prevent the deposit of soil-making matter during the period of its submergence?
There are evidences, in the elevated beaches of the Oregon and Washington coast, of great changes of water
