The U. S. Coast and Geodetic Survey Precise Level "is constructed without regard to cost, extreme accuracy being the governing consideration. This fact accounts for the seemingly high price, which is for the complete instrument, with two achromatic eye–pieces, graduated and chambered level–vial having a value of 2 seconds per division. Completed packed, with extra heavy tripod...$300." Thus wrote G. N. Saegmuller, proprietor of Fauth & Co., describing the Precise Level that had been developed by E. G. Fischer and his colleagues in the Instrument Division of the Coast and Geodetic Survey. This example, marked "FAUTH & CO. WASHN. D.C. 2239" was made between 1900, when the form was introduced, and 1905, when Fauth went out of business. It belonged to the University of Missouri at Columbia.
To minimize changes due to temperature variation, Fischer's team developed an iron–nickel alloy with a very low coefficient of expansion. They also placed the telescope tube within a slightly larger tube, and sealed the openings between the tubes with chamois leather collars. To minimize disruptions caused by changes in weight or pressure upon the ground, Fischer's team mounted the level above the telescope. A mirror, mounted above the level, reflects an image of the bubble into a tube at the left side of the telescope. Thus, while the surveyor's right eye looks through the telescope to the distant rod, his/her left eye can see both ends of the level vial.
The Fischer level was Fauth's third precise level. The first was similar to the instrument that Kern had shown at the 1876 Centennial Exhibition held in Philadelphia. The second, unveiled in 1879, was based on a design originating in Vienna, Austria, and developed in the Instrument Shop of the Coast and Geodetic Survey, which was then under Saegmuller's direction.
Ref: E. G. Fischer, "Description of Precise Levels Nos. 7 and 8," Report of the Director of the United States Coast and Geodetic Survey (1900), Appendix 6.
George N. Saegmuller, Descriptive Price–List of First–Class Engineering & Astronomical Instruments (Washington, D.C., 1903), pp. 60–61.
Randall Brooks and Heather Bajdik, "Precise Levels in Surveys of North America," Rittenhouse 10 (1996): 48–57.
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