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1899, the party as organized being similar to that of the preceding season. The field work which remained was to remeasure a portion of the line, place the monuments, cut out the true line, and secure additional data for the map.

The line was divided into four sections, reference to which will be made hereafter. Three of them were controlled by triangulation, but the fourth, or northernmost section, not being so controlled, it was decided to remeasure that section with the stadia, and also to make a careful comparative measurement with a steel tape. The measurement with the steel tape served not only to check this section of the line, but was also used as a basis of comparison with the stadia measurements and to determine a stadia factor, which was afterwards applied to all of the stadia work.

The measurements of the northernmost section were first made, and the northern terminal point of the line determined. The party then started southward, and the monuments were established, marked, and witnessed in accordance with the instructions. The topography was also sketched, but as the territory through which the line ran was for the most part covered with timber, it was impossible, without delaying the work beyond the limit of the available funds, to cover more than a narrow belt. This work was completed October 5, 1899, and after a short service in another locality Mr. Reaburn reported to the office in Washington for the preparation of the final notes and plats.

LATITUDE, LONGITUDE, BASE LINE, AZIMUTH, AND TRIANGULATION.

In the following pages is given a short account of the methods employed in establishing what may be termed "the control" for the boundary line.

By combining the results of the latitude, longitude, and azimuth observations with the base-line measurement, the position on the earth's surface and the length and true direction of a line were determined. Through a system of triangulation based on the line thus established the positions of points near the boundary line were computed, as well as the distances and directions between these points.

LATITUDE.

The new county court-house at Spokane having been built very close to the longitude pier of the United States Coast and Geodetic Survey of 1888, the latter could not be used as a latitude pier. A new pier was therefore built 67.4 feet east of the longitude pier, where an unobstructed view of the meridian could be obtained. (See Pl. IV.)

A Fauth combined transit and zenith telescope (No. 534) was mounted on this pier, and in August, 1896, observations for latitude, by the Talcott method, were made by Mr. S. S. Gannett. Pairs

The

of stars were selected from Safford's Catalogue of 2018 Stars. apparent day places, however, were obtained from the Berliner Jahrbuch whenever possible; otherwise, they were computed by the usual methods, as explained in the American Ephemeris.

Fifty-nine observations upon twenty-seven pairs of stars gave a weighted mean value for the latitude of the pier of 47° 39′ 51.46 0.13. The results for different nights and for different pairs of stars are given in the following table:

Results for latitude, Spokane (Washington) Station, 1896.

[S. S. Gannett, observer and computer.]

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ASTRONOMIC PIERS IN COURT-HOUSE GROUNDS AT SPOKANE, WASHINGTON.

U. S Geolog cal Survey latitude pier in right foreground: U. S Coast and Geodetic Survey longitude pier behind figure of man.

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