The Henry Mountains have been visited only by the explorer. Previous to 1869 they were not placed upon any map, nor was mention made of them in any of the published accounts of exploration or survey in the Rocky Mountain region. In that year Professor Powell while descending the Colorado River in boats passed near their foot, and gave to them the name which they bear in honor of Prof. Joseph Henry, the distinguished physicist. In 1872 Prof A. H. Thompson, engaged in the continuance of the survey of the river, led a party across the mountains by the Penellen Pass, and climbed some of the highest peaks. Frontiersmen in search of farming and grazing lands or of the precious metals have since that time paid several visits to the mountains; but no survey was made of them until the years 1875 and 1876, when Mr. Walter H. Graves and the writer visited them for that purpose. They are situated in Southern Utah, and are crossed by the meridian of 110° 45′ and the thirty-eighth parallel. They stand upon the right bank of the Colorado River of the West, and between its tributaries, the Dirty Devil and the Escalante. At the time of their discovery by Professor Powell the mountains were in the center of the largest unexplored district in the territory of the United States—a district which by its peculiar ruggedness had turned aside all previous travelers. Up to that time the greater part of the knowledge that had been gained of the interior of the continent had been acquired in the search for routes for transcontinental railways; and the cañons of the Colorado Basin, opposing more serious obstacles to travel than the mountain ranges which were met in other latitudes, were by common consent avoided by the engineers. The same general causes which have rendered the region so difficult of access and passage have made it a desert, almost without economic value. The physical conditions of elevation and aridity which have caused it to be so deeply carved in cañons, have prevented the streams with which it is scantily watered from being bordered by tracts of land which can be irrigated; and agriculture without irrigation being in that climate an impossibility, there is nothing to attract the farmer. As will be explained in the sequel, the mountains offer no inducements to the miner of the precious metals. There is timber upon their flanks and there is coal near at hand, but both are too far removed from other economic interests to find the market which would give them value. It is only for purposes of grazing that they can be said to have a money value, and so distant are they at present from any market that even that value is small.