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Show 6 The cistern and aneroid barometers, with the psychrometer, were read at regular intervals in camp and at all points that would serve to indicate the relief of the country. About six thousand square miles of a very difficult mountain and canon country was mapped here. The accuracy of the work depends upon the triangulation and the latitude- cheeks. The former was entirely upon natural objects, the peaks of the Wahsatch range, the Henry Mountains, Navajo, and prominent mesas, and made with the gradieuta by Mr. Thompsou, who has shown more than ordinary skill and energy in performing rapid and accurate work. We derived much assistauce from Mr. Howell, whose investigations in geology were necessarily carried on in intimate connection with the topography. The sextant observations were made entirely by myself, and the average probable error of the results is about ten seconds of arc. More time was taken in this part of our field of operations than allowed by your instructions, but this was necessitated by the obstacles encountered. In the month of June we found the high passes of the Wahsatch Range blockaded with snow and mud, and the streams on the eastern slope were swift, cold, aud deep, causing serious detentions. Later in the season we had worked our way southward into the cailon country, in which progress was necessarily slow, and a scarcity of grass and water added to the difficulty of traversing the country. At this time two of my packers deserted with thirty- two mules, and caused a further delay of about twenty flays. The time was usefully employed, however. The full working force kept the field as usual, aud although I had not intended to give the time here, the work done in consequence could not well have been dispensed with. The recovery of the mules, with the men who ran them off, cost me a chase of four hundred miles, the return being accomplished in two hundred more, over the wildest part of a difficult country. We encountered considerable hardship during this part of our season's work, being frequently without good water, and sometimes without any. At oue time we subsisted for seven days upon hard corn, brought along for the mules, and taken from them when they could ill spare it. It was not possible to sacrifice close work to the pressure of time, as the devious track which covered so much ground was forced upon us by the difficult nature of the country. A portion of the results of this part of the season's work are already published in Atlas sheets Nos. 50 and 59, and Mr. Howell will report upon the geology and mineralogy of the country so far as observed by him. From the crossing of the Colorado to Fort Wingate, the most direct route was taken and no attempt was made to map the country through which we passed. The trail was carefully meandered, however, the topography adjacent sketched in, and frequent bearings taken as checks • upon prominent poiuts, with the usual latitude- checks for the camps and the observations with cistern barometer, aneroid, and psychrometer. The primiary object here was celerity of motion, the survey recommencing at Fort Wingate. The length of measured meander line was about two hundred miles. Soon after leaving Fort Wingate Mr. Thompson was detached by your order, with a small party, to carry a system of triangles over the grouud covered by my own and the other parties then operating together in ^ ew Mexico. This work was successfully accomplished. Base lines |