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Show 1218 REPORT OF THE CHIEF OF ENGINEERS. The latitude and longitude and altitude of the main astronomical stations will be given in volume II of the quarto reports, now passing through the press. It has not been found necessary to occupy further main astronomical stations for the purpose of checking positions determined by other means in the prosecution of work of 1877) but upon the completion of the observatory at Ogden and those contemplated- one at Denver, Col., another on the western slope of the Sierras, a number of points to the north and south of the present line of the Pacific Railroad, i. e., in Oregon, Idaho, Montana, Texas, New Mexico, and Arizona- may be occupied. GEODETIC AND TOPOGRAPHICAL. The sketches showing the triangulation in the Colorado, Utah, and California sections are added to as computations progress, and from time to time, as it covers a number of the regular atlas sheets, will be published, as well as the geographical positions, obtained by triangulation, of prominent points. The number of triangulation stations of the highest grade increases each year, and especially in areas where more numerous observations become necessary in order to gather data for delineation on maps of the larger scales. As usual, the areas occupied in the expeditions of 1876 aud 1877 follow strictly those authorized by the Chief of Engineers and the honorable the Secretary of War, in pursuance of projects submitted by the officer in charge, and are all laid within that part of the territory of the United States lying west of the one- hundredth meridian, as shown upon the progress map, and over which it is contemplated that topographical surveys in detail commensurate with the character and development of the various sections shall be prosecuted to completion. The topographical assistants are now required to add to their notes careful data showing the natural resources of the region traversed, in order to collect information as to the general character and value of the areas still belonging to the Government, and it appears that the relative areas of arable, timber, grazing, mineral, and arid lands may be described and delineated. The noticeable topographical results inaugurated during the year are about Lake Tahoe, in the Sierra Nevada, the topography of which, from data now gathered, warrant a projection on a scale of 1 inch to 1 mile, which has been completed at the hands of a special party engaged upon the high peaks and along the divides of the water courses of this peculiarly interesting lake region. The plane- table sheets covering the entire Comstock mining district are drawn upon a scale of 1 inch to 500 feet, and will, after reduction, serve as a complete and connected contour map of this region so abundant in the precious metals. As usual, when practicable, connections have been made with main and minor points of the land survey and monuments built in all cases of due importance. The areas covered by the expedition of 1876 are noted upon the progress map as parts of atlas sheets 47, 48, 56, 61,62, 70, 77, and 78. Portions of the following basins are embraced, the " Great Interior Basin, v and those of the Arkansas and Bio Grande Rivers, as well as the headwaters of a number of streams lining the western slopes of the Sierra Nevada between the latitudinal limits noted on the progress sheet. The gauge of the success of the expedition is better shown by the number and character of the observations made at the main geo- |