In the light of Mr. Gilbert's discoveries, however, everything is clear. The tremendous _débâcle_ which he has brought within the range of scientific vision would naturally produce just the condition of things which is so puzzling at Pocatello. Coming down through the restricted channel with sufficient force to roll along boulders of great size and to clear them all out from the upper portion of the valley, the torrent would naturally deposit them where the current was first checked, a mile below the lava cliffs. The plunge of the water over these cliffs would keep a short space below clear from boulders, and the more moderate stream of subsequent times would fill in the depression with the sand and gravel now occupying it. What other effects of this remarkable outburst may be traced farther down in the Snake River Valley I cannot say, but it will be surprising if they do not come to light and help to solve some of the many geological problems yet awaiting us in this interesting region. It should have been said that during the formation of the 625-foot, or so-called Provo shore-line, glaciers descended from the cañons on the west flank of the Wahsatch Mountains, and left terminal moraines to mark the coincidence of the Glacial period with that stage of the enlargement of the lake. Evidences of a similar coincidence are to be found on the high-level terraces surrounding Lake Mono, to which glaciers formerly descended from the western flanks of the Sierra Nevada. The ancient shore-lines surrounding Lakes Bonneville and Lahontan bear evidence also of various other episodes in the Glacial period. Evidently there were two periods of marked increase in the size of the lakes, with an arid period intervening. During the first rise the level of Bonneville attained to within ninety feet of the second, and numerous beaches were formed, and a large amount of yellow clay deposited. Then it seems to have been wholly evaporated, while its soluble mineral matter was precipitated, and so mingled with silt that it did not readily redissolve during the second great rise of water. Partly on this account, and partly through the influence of the outlet into the Snake River, the lake was nearly fresh during its second enlargement. _European Facts._ In Chapter VI it came in place to mention many of the facts connected with the influence of the Glacial period upon the drainage systems of Europe. We there discussed briefly the probable influence of the ice-obstructions that extended across the mouths of the Dwina, the Vistula, the Oder, the Elbe, the Weser, and the Rhine. The drainage of the obstructed rivers in Russia was perhaps turned southward into the Caspian and Black Seas, and then assisted in forming the fertile soil of the plains in the southern part of that empire.