Identifier: reportofboundary00inte (find matches)
Title: Report of the Boundary commission upon the survey and re-marking of the boundary between the United States and Mexico west of the Rio Grande, 1891-1896 ..
Year: 1898 (1890s)
Authors: International boundary commission (United States and Mexico) 1882-1896. (from old catalog)
Subjects:
Publisher: Washington, Govt. print. off.
Contributing Library: The Library of Congress
Digitizing Sponsor: Sloan Foundation

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crometer readings, and the known length ofthe measured offset, enabled the heliotroper to determine his previously estimated distance fromthe instrument, and to compute quite accurately a new offset from the point last established. This process was repeated until the angle between the two heliotropes measured less than twomicrometer divisions (2.5), when the observations were completed by a measurement of thisangle by 27 pointings, in sets of 3 alternately, with eyepiece micrometer on the two heliotropes.Using this measurement and the more accurate stadia distance afterwards determined by thetopographical party, the small offset from the station as marked to the true line was computedand furnished to the monument party previous to the erection of monuments. Sometimes as many as seven intermediate points were established from a single instrumentstation; sometimes the instrument was moved up to every new station as established, and occa-sionally it was lined in between two fixed points.
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UNITED STATES AND MEXICAN BOUNDARY. 121 The time occupied in establishing au iutermediate station within 2.5 of the line, and theumeasuring the final angle, varied from about thirty to sixty minutes. From Monument 175 to Monument 127 each original monument, except Monument 150, wasvisible from the preceding one, and the line was traced by placing a heliotrope over one monumentand running toward it from the preceding one. Monument 150 was not visible from Monument 100, and the peak which intercepted the view,Cerro de la Lesna, had sides so nearly vertical and a crest so narrow and disintegrated that itwas practically impossible to set up an instrument on it in order to line in a point on its summit.Accordingly, a strong geodetic connection was made around the south side of the peak, by meansof which points on the line joining the two monuments were established on both its eastern andwestern base, as well as on its summit. (For details of this connection see report of Mr. John F.Hayford

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