_Below Split Mountain Cañon._--Lying along the Green, and between the foot of Split Mountain Cañon and the mouth of the Uinta, are 50 square miles of arable land. Some portions of this may be subject to inundations at times of extraordinary floods, but the greater part is above high water mark. Green River here carries sufficient water to irrigate many times this amount of land, and while the cost for the construction of suitable dams and canals would be greater than on smaller streams, neither this nor the engineering skill required would be beyond the resources of any ordinary settlement. _Gunnison Valley._--In Gunnison Valley, below the foot of Gray Cañon, are 25 square miles of arable land. The cost of constructing the necessary irrigation works at this point would be greater than above the mouth of the Uinta, but still not beyond the ability of a colony. Green River flowed in Gunnison Valley in September, 1877, 4,400 cubic feet of water per second, enough to irrigate at the standard adopted 860 square miles. There seems to be no arable land to which it is possible to take this great surplus, and probably for many years to come it will be suffered to flow “unvexed to the sea”. The area colored on the map is much greater than above indicated. The selections of irrigable lands will be made on either side of the river, in patches, within the colored district. THE GRAND RIVER. The Grand River has but a small amount of arable land along its course in Utah, and flows for most of the distance in a close cañon. The volume of the stream, about 40 miles above its junction with the Green, was measured in September, 1877, and found to be 4,860 feet per second. It is probable that selections can be made to the extent of 40 square miles from the areas colored on the map. THE SAN JUAN RIVER. But little is known concerning the arable lands or volume of water in the valley of the San Juan. It flows for the most of its course through Utah in a cañon, and all the arable land is thought to be so much subject to overflow that cultivation is impracticable. OTHER STREAMS. A few smaller streams are also tributary to the Colorado and Green within the Territory of Utah, but they mostly flow in deep cañons, are often dry in some portion of their course during every year, have at best only a few acres of arable land anywhere along their courses, and have been omitted in this report. The following table gives a summary of the facts relating to the flow of the several streams and the amount of arable and irrigable lands in the districts described above: