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Show 47 APPENDIX F. METEOROLOGY AND HYPSOKETRY, FJELD- 8EA8OX OP 1874, BY LIBUTBNANT W. L. MARSHALL, CORPS OF ENGINEERS. UNITED STATES ENGINEER OFFICE, GEOGRAPHICAL EXPLORATIONS AND SURVEYS WEST OF THE 100TH MERIDIAN, Washington, D. C, April 30,1875. SIR: I have the honor to submit the following report npon the barometric work of the past season, together with a brief description of the system of observation, record, and redaction in ase npon the survey since I have been in charge of this branch of the work. . - - >^~- The present efficient state of this department is largely doe to the efforts of Lieut. R. L. Hoxie, Corps of Engineers; the methods prescribed by him, both for field and office, having been adhered to, with modifications, by myself and assistants. FIELD- OBSERVATIONS, COMPARISONS, RECORDS, AND TRANSCRIPTS. Before taking the field, the office- standards were compared with those of the United States Army Signal- Office, and the remainder of the instruments with these office-standards, to determine the errors of the barometers and thermometers. From the office, the instruments were carefully transported to the field by hand, to guard, as far as practicable, against forced changes in their relative errors. Upon the arrival at Pueblo, Colo., they were all again compared hourly pending the organization of the expedition, which furnished a means of checking the errors already determined at Washington, D. C, and of deducing the amount of change in the adjustment of such barometers as were affected by transportation. As soon as the organization of the field- parties was effected,, the barometric observers - were carefully instructed by yourself and by me in their duties, and in regard to the care, repair, and transportation of barometers and meteorological instruments. Each field- party was provided with two of Green's mercurial cistern- brometers, reading by vernier to 0.002 inch; two sets of psychrometers; from two to five aneroid barometers, with the necessary pocket- thermometers to be used in connection with the aneroids, and with one box of implements and eight empty tubes for refitting broken instruments. Every person who had charge of a barometer was furnished with printed instructions as to its use, and with the necessary ruled and headed blank books and forms of record for intelligibly recording his observations; and it was made imperative that all observations should be recorded upon these forms, to prevent loss and confusion. The observations taken by members of the field- parties were: 1. Cistern- barometer and psychrometer observations in camp every three hours, or at 7 a. m., 2 p. mM and 9 p. m., at which hours also all meteorological instruments of the party were compared for determining the altitudes of camps and to furnish the means of detecting changes in instrumental errors. 2. Cistern- barometer and psychrometer observations upon peaks and topographical stations, simultaneous with observations in camp. 3. Aneroid and thermometer readings, in connection with the odometer at meander-stations, for securing definite profiles of the roads, trails, & c, and the gradients of passes. At important points along meander- lines, at towns or settlements, aud upon the summits of divides, & c, cistern- barometer and psychrometer were also read. * 4. Aneroid and thermometer readings, taken by various members of the different parties at important points which can easily be identified and located upon the map without the aid of the topographer. In addition to the above readings, taken for hypsometric purposes alone, general meteorological observations, such as are prescribed by the Smithsonian instructions, were taken and recorded, and furnish valuable information in regard to the climate and meteorological conditions of the regions surveyed for the time of the year the parties were in the field. Whenever a camp was established for several days, hourly observations were taken, from which tables of horary corrections have been formed, and used in the reduction of the aneroid work and isolated observations. Such tables were secured, including the astronomical station of 1873, for Hughes, Georgetown, Colorado Springs, Pueblo, Labran, Trinidad, Fort Garland, and Pagosa Hot Springs, in Colorado Territory; Cimarron, Fort Union, Las Vegas, and Santa Fe\ in New Mexico. A permanent station was established at Pueblo, Colo., and continuous observations have been voluntarily taken during the past winter by Mr. S. F. Parish for the use of the survey. Exclusive of those for the hourly work, the blank books aud forms for the record and reduction of these observatiens are six in number. 1 have appended hereto copies |