The estimate of 219 miles of cultivable land on the Delta Plain includes 15 miles that will probably never be irrigated, but may nevertheless be farmed. The total area of the Weber basin (including the whole plain from Bonneville to Centerville, and excluding the main body of Kamas Prairie) is 2,450 square miles; 4³⁄₄ per cent. of the area is now under cultivation, and 10¹⁄₃ per cent. is susceptible of cultivation. * * * * * The _Jordan River_ is the outlet of Utah Lake, and runs northward, entering Great Salt Lake at its southeastern angle. On the right it receives a number of large tributaries from the Wasatch Range. The largest tributary of Utah Lake is the Provo River, which rises in the Uinta Mountains close to the heads of the Weber and Bear. From the mouth of its mountain cañon the Provo enters Kamas Prairie, and it hugs the south margin of the plain just as the Weber hugs the north margin, passing out by a narrow defile at the southwest corner. At one time in the history of the prairie the Provo flowed northward through it and joined itself to the Weber. The surface of the prairie was then lower than now, and the sand and gravel which the river brought from the mountains accumulated upon it. Eventually the Provo built its alluvium so high that its water found a new passage over the wall of the valley. The new channel, affording a more rapid descent than the old, quickened the current through the valley, and caused it to reverse its action and begin the excavation of the material it had deposited. So long as the river built up its bed, its channel was inconstant, shifting from place to place over the whole plain; but so soon as it began to cut away the bed, its position became fixed and the plain was abandoned. The river now flows in a narrow valley of its own making, 150 feet below the surface of the plain. As a result of this mode of origin, Kamas Prairie slopes uniformly from the Provo to the Weber, and it would be an immense undertaking to irrigate it with the water of the Weber. But the Provo River can be returned to its ancient duty with comparative ease. A few miles of canal will suffice to carry its water to the upper edge of the plain, and thence it can be led to every part. Already a small canal has been constructed and its enlargement may convert the whole prairie into a meadow. Thus the prairie, although part of the drainage basin of the Weber, belongs to the irrigation district of the Provo. The Provo next follows a narrow rock bound valley for 7 miles, being skirted by bottom lands that admit of some farming. It then enters Provo Valley, an opening about as large as the last, and favored by a warm climate that permits the growth of breadstuffs. Thence to Utah Valley it follows a deep, close cañon.