Tantalus Creek drains the northern portion of the eastern slope of the Aquarius Plateau. It enters a close cañon at 8,000 feet altitude, and continues in cañons until it has passed through Water Pocket Fold. It then flows along a desolate valley at the foot of the fold until it joins the Fremont River. During the warmer months the water in this creek is usually absorbed and evaporated before reaching its mouth. In the valley at the foot of Water Pocket Fold are about 10 square miles of arable land; but the almost inaccessible situation of the valley and the desolation and ruggedness of the surrounding country may present insurmountable obstacles to its settlement. Curtis Creek, the northern tributary of Fremont River, is formed by the union of several smaller streams that rise in the Wasatch Plateau. Debouching from the plateau, these branches flow across what is known as Castle Valley, and here, at an altitude of 6,000 feet, are 25 square miles of good arable land. They were measured in September, 1876, and gave an aggregated flow of 47 cubic feet per second. As they derive a greater part of their waters from the melting snows on the plateau, double this amount, or 94 cubic feet, would not be an overestimate of the volume during the irrigating season. After the union of these branches, the united stream flows in a deep cañon until near its junction with the Fremont River in Graves Valley. Both Curtis Creek and the Fremont receive some accessions to their volume from springs in the cañons through which they flow above this valley. If all the water in their upper courses should be used to irrigate lands in Castle and Rabbit Valleys, a sufficient amount would be returned to their channels by percolation to irrigate, with the addition of the accessions in the cañons, all the arable land in Graves Valley. THE SAN RAFAEL RIVER.