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Show 40 of aneroid and odometer, whereby definite profiles are secured; also, the method of reduction of the aneroid work, whei- eby the effect of instrumental errors are nearly eliminated from the final results. These observations, many hundreds in number for each party, have all been corrected for instrumental errors and Uorary oscillations, carefully computed, and the altitudes written upon the plats. AZIMUTHS. The tria^ gulation- stations all being very far above the upper limit of tree- growth, and the peaks themselves seldom visible from any convenient camping- place where wood for fires could be obtained, it was generally impracticable, from cold, to take observations at night for azimuths of sides of the main triangles. However, at Simpson's Peak, a lofty mass above 14.000 feet altitude, at the head of the Rio Los Pinos, which I have named, with your permission, iu honor of Col. J. H. Simpson, Corps of Engineers, who has done so much in the way of western exploration, quite an extended series of observations on Polaris were made by myself and Mr. Nell for azimu'h; the time being determined by sextaut and watch, and the observations taken near elongation. At camps, the usual observations on Polaris at elongation for magnetic declination ; and for azimuth, when * e relied upon latitude and azimuth for the location of our camps, were taken, and have been computed. These results of single observations for magnetic declination, taken by the various parties of the survey since its organization at hundreds of places in the interior where this element of terrestrial magnetics baa not been known, with nearly as close an approximation to accuracy as given even by our short needles and the coarsely- graduated arcs of our meander- theodolites, should vow be . sufficiently numerous to be of great value in the construction of general magnetic charts. During the past season, I have always endeavored to have this element more accurately determined by attaching a needle to the telescope of the 8- inch transit used on our \ triangulution- stations, and causing to be measured as accurately as possible the angle between the magnetic meridian and a side of a main triangle, the azimuth of which is quite accurately given by the computation of the triangles. The azimuth of the base- lines at Pueblo and Trinidad, in the measurement of which my party participated, was determined by elaborate observations made by Dr. Kampf with an 8- inch theodolite, in connection with au astronomical transit. Respectfully submitted. WM. L. MARSHALL, Firat Lieutenant of Engineers. Lieut. GEO. M. WHEELER, Corps of Engineers, APPENDIX B. EXECUTIVE REPORT OF LIEUTENANT P. M. PRICE, CORPS OF ENGINEER8, ON THE OPERATIONS OF PARTY NO. 1, SECOND DIVISION, FIELD- SEASON OF 1874. . UNITED STATES ENGINEER OFFICE, GEOGRAPHICAL EXPLORATIONS AND SURVEYS WEST OF THE 100TH MERIDIAN, Washington, D. C, March 17, 1S75. SIR: I have the honor to submit the fol lowing report upon the operations of parly No. 1, second division, while under my charge, dnriug the field- season of 1874 : Upon taking charge of the party at Santa Fe", N. Mex., on the 3d of October, 1874, \ t* personnel was as follows: Gilbert Thompson, chief topographer; Frank Carpenter, assistant topographer; Dr. Oscar Loew, chemist and mineralogist; L. H. Hance, meteorological observer; A. J. Tweed, odometer- recorder; two packers; one herder; and one cook. The first work to be performed was the measurement and development of a base- line at this point. On account of the difficulty of finding, in the immediate vicinity of Santa Fe\ a position snitable for this purpose, the plateau south of Tetilla Peak, and abont fifteen miles southwest of Santa Fe\ was selected. The base- line was measured twice with a compensated steel tape, f> 0 feet in length, under a pull of twenty pounds; t he tape being set for temperature on the measurement of each length. Pegs were driven at distances of 200 feet apart, and at less distance when required by the nature of t he ground. The difference of level between the consecutive pegs was afterward determined by leveling with a Y- level, and the corrections necessary to reduce" the measnred distance4to a horizontal distance calculated and applied. The two measurements R i ve 19391.027 feet and 19391.073 feet, a difference of 0.046 foot, and a mean of 19391.05 f e e t . The base- line was developed, and connected by good triangles with the astronomical |
