OCR Text |
Show 135 The party was in the field one hundred and forty- three days. A system of triangles was closed over an area of about 8,000 square miles of territory, and the topography of this area, with about a third as much more obtained by running meanders exterior to the system, was, as far as practicable, carefully studied and can be mapped. The parallel ranges of mountains, with but 15 or 20 miles between their crests, and these marked with well- defined points, afforded an excellent opportunity for carrying on the triangulation. A base, 6.78 miles in length, was measured in Panamint Valley, where we were able to find a nearly level and favorable surface, and well- conditioned triangles enabled us to include two prominent mountain stations ( Telescope and Malurango Peaks) in the first extension. This system was definitely connected with that of the Los Angeles base by the two parties occupying in common Whitney's, Olancha, and Owens Peaks. In the measurement of the base an instrumental line was laid out between the extremities and marked by small white flags planted at intervals of fifty paces, obstructions and irregularities of surface were removed, and the line carefully measured with a spring- steel tape- line, compensated for temperature. The line runs a little west of north from the south end, which is near the center of the valley, and about one- fourth of a mile north of the direct road from Shepperds Cation to Panamint Cafion. This end is marked by a rough- hewn stone monument, projecting 15 inches above the surface, reotangular in shape, 6 by 8 inches, and 1875 inscribed on the side away from the base. In this valley our survey was also connected with the land- eurvey, a three- point station being made at section- corner of ranges 42 and 43, township 20, sections 7,18,12, and 13. This section- corner is situated 5 miles, and bears north 70° west, from the northern extremity of the base, which is a monument of rough stones. A series of observations was made to determine the azimuth of the base, and of sextant observations for latitude at the south end. In addition to this, sextant observations were taken at sixteen other points, which were also connected by instrumental bearings with the triangulation. In all, thirty- six sextant latitude stations were made, and complete observations for azimuth of sides of triangles at four different points. Magnetic variation was determined by observations on Polaris; thirty- nine results have been recorded, including those determined at the apices of triangles, where the difference between the magnetio and true azimuth of one of the sides was, whenever practicable, carefully determined, the true azimuth resulting from computations afterwards made. Eighteen triangnl at ion- stations and thirty- two topographical stations, including the eighteen triangulat- ion- stations, were made. * At starting, the party was well supplied with instruments for taking the meteorological observations required ; both our barometers were out of order by July 12, but new tubes being received at Panamint in August enabled us to use this instrument for the remainder of the season, good comparisons for error being made on our return. The party was unfortuuate in that, from breakage or loss, the full set of meteorological instruments was not carried throughout the season ; and the results of the observations taken have been curtailed on account of this; the meteorological observations were taken throughout to conform to your written instructions, and, together with the odometer record, duplicated and compared in the field. Eighty- two cistern- barometer stations were made, and. four hundred and sixty- two aneroid stations in addition. The principal roads and trails were meandered, and a table of distances for these, with remarks as to wood, water, & c, prepared in the field. ft Twelve hundred and sixty- one miles were meandered and 611 traversed but not meandered; thirty- three point- stations were made as checks, and six hundred and seventy- two other stations upon meander- lines. The instruments used werethe sextant, Stack pole & Brother's, for latitude; Wurde- . mann theodolite, graduated to read to 10" of arc, for triangulation; Wurdemann graduated and Young & Son's small transit, for topography and meander work; cistern and aneroid barometer, with wet and dry bulb, and maximum and minimum and pocket thermometers, for meteorological observations ; the compensated steel tape for accurate and the odometer for road measurements. Short meanders were sometimes made with the pocket- compass. A number of mining- camps were visited, and everywhere the party met with the kindest treatment from the people of the country and a willingness to impart information that proved of great value to us in traveling. Especially are we indebted to Capt. A. B. MacGowan and the officers at Camp Independence, aud Mr. Maclean, the superintendent of the Cerro Qordo Freighting Company, for assistance rendered us. The members of the party, with scarcely an exception at any time, worked with a unison aud cheerfulness that is a pleasure for me to record. Very respectfully, your obedient servant, R. BIRNIF, JR., Firet Lieutenant Thirteenth Infantry. Lieut. GKO. M. WHBELVR, Corpe of Engineers, in charge. |