presence of water, and is furthermore attractive by reason of the picture-writings on the walls. He has now to cross the Blue Gate flexure, and to do this he leaves Temple Creek a little below the mouth of its cañon. Seeking once more the guidance of a trail, he journeys southeastward over the gypsum and sand of the Flaming Gorge Group to a pass which from a distance he has detected in the monoclinal ridge marking the Henry’s Fork conglomerate. Through this pass Tantalus Creek sometimes runs on its way to join the Dirty Devil, and he may find a stream of muddy water; but the bottom is more likely to be dry with the exception of a few pools. Passing through the gap he finds before him a similar opening in the Tununk Ridge, and beyond that a break in the Blue Gate Cliff. From Tantalus Creek he ascends to the pass in the Blue Gate Cliff, and climbing to the summit of a sharp divide in the shales descends again to Lewis Creek, which there follows a cañon through the Blue Gate Plateau. Here he finds bowlders of the Henry Mountain trachyte—for Lewis Creek rises in the Henry Mountains—and a few hours’ ride toward the sources of the stream brings him to the base of Mount Ellen. _Distances._ From Salt Lake City to Salina 155 miles. From Salina to Fish Lake 38 miles. From Fish Lake to Rabbit Valley 27 miles. From Rabbit Valley to Temple Creek Cañon 27 miles. From Temple Creek Cañon to Lewis Creek 18 miles. Thence to the base of Mount Ellen 10 miles. ——— Total from Salt Lake City to the Henry Mountains 275 miles. CHAPTER II. THE STRUCTURE OF THE HENRY MOUNTAINS. The mountains stand within the province of the great flexures, but are independent of them. Fifteen miles to the westward runs the Waterpocket flexure. Thirty miles to the north is the San Rafael fold. At the east the strata rise toward a great uplift, of which the full form is unknown. But where the Henry Mountains stand the rocks are unaffected by these disturbances. They have a uniform dip of about 45′ to the northwest, and form a perfect datum-plane from which to measure the magnitude of the displacements which have given rise to the mountains. The mountains are composed of a large number of parts which are in a certain degree individual and homologous. By the generalization of the characters of those parts a conception has been obtained of a _type structure_ to which the entire series of phenomena has been referred. In laying the material before the reader, the following plan will be followed: First. The type of structure will be briefly set forth. Second. The phenomena by which the type is at once demonstrated and illustrated will be described in detail. Third. The type of structure will be discussed.