Thus all the deep channels were filled and all the islands deeply overrun with ice, while the immense bergs launched from the shore and carried by the winds and currents southward were probably not melted until they reached the tropical latitudes. Thus, when the whole circulation of the Pacific waters are taken into account, it will be seen that their temperature during the ice age must have been considerably lowered. The movement of ice-sheets on the Pacific slope was probably local in character, and not connected with the movement of ice on the eastern sides of the mountains. From what I have seen of the vast territory lying between the Sierra Nevada and the Rocky Mountains it appears that it obtained much heavier ice-fields than generally supposed. Professor Geikie in his lectures says of this region that during the glacial age, “in the Second Colorado Canyon, the sides were completely glaciated from bottom to top. These walls are from 800 to 1,000 feet high, and at the thickest point the glacier was 1,700 feet thick”; and he says that “the country around Salt Lake was covered with ice, for the rocks about there show the action of ice, and that the bones of the musk-ox are found there.” This vast area of ancient ice, although subject to little movement in its interior basin, still, in whatever movement it may have had, must have found its main outlet through the Grand Canyon of the Colorado. For in no other way can we account for the erosive forces necessary to excavate that immense chasm. Not even the mighty torrent that carried off the waters of the melting ice-sheets that covered the interior portion of the continent could accomplish work of such magnitude. According to Professor Geikie’s observations the Second Colorado Canyon was filled with glaciers during the ice age. Therefore, it seems that these glaciers must have flowed down into the Grand Canyon, and there united with glaciers flowing from more northern regions. An account of a collecting expedition to Lower California by G. Eison, in 1895, describes ancient moraines at the extremity of the peninsula as being prominent, large, and steep. This region lies under the tropic of Cancer, and 8° south of the mouth of the Colorado River where it empties into the Gulf of California. Hence it appears that the temperature of that portion of North America during the ice age was favorable for the great glacier of the Colorado Canyon to have flowed into the Gulf of California. The wide, shallow basins of Utah and Nevada were filled with the water from the melting ice-sheet on the breaking up of the ice period, and the lakes so caused remained for a considerable time after the disappearance of the ice. But, owing to the great evaporation and light rain-fall of that region, the lakes gradually shrank away, the filling and emptying of the lake basins being governed by the cold and mild epochs.