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Show FISH LAKE. 263 been unable to discover sufficient evidence to sustain ether view. Although the traces of ancient glaciers are conspicuous in the vicinity, nothing can be more sharply defined than the places where they terminated; and we are able to affirm confidently, by a comparison of places in close juxtaposition, that in one place the sculpture is due to glaciation and in another it is not. It does not appear anywhere in this part of the plateaus that the glaciers ever extended much below the 9,000 feet level, for at about that level the terminal moraines cease and give place to other forms of sculpture. As regards the possibility of a sunken block between two faults, it seems to me that the evidence is not sufficient to establish it, and there is decided evidence that it is an ancient valley of erosion, having its main features marked out and partially developed before the present elevation of the country had been reached. At the southwestern extremity is a low divide, scarcely 30 feet above the water level, which forms the local watershed between the Colorado drainage system and that of the Great Basin. At present the lake drains into the Colorado system; but at no distant epoch it apparently drained into the basin system, flowing over this low divide. Its ancient channel, leading down into Grass Valley (tributary to the Sevier River), is as distinct and unmistakable as if it had dried up only a few years ago. Mr. Howell, who recognized this channel and its obvious meaning, supposed that the barrier now forming the divide had been produced by morainal debris brought down from the Fish Lake Plateau and deposited athwart the channel. More careful scrutiny, however, shows that the barrier consists of volcanic rock in place. Hence it appears that the course of the drainage has been reversed. Originally it flowed out of the lake to the southwest; but as the gradual uplifting went on the whole lake basin was tilted, so that it began to flow out of the opposite end and over a low barrier to the east and southeast. A very slight tilting only was required to effect the change; and a drop of 40 or 50 feet on the western side would again reverse it to its original channel and pour it down the Awapa wall into Grass Valley. A journey along the bank of the lake towards its outlet is instructive as well as entertaining. The trail (I believe there is now a wagon-road) leads along the base of the plateau wall, rising more than 2,000 feet above |