. Bulletin - United States National Museum. Science. w If. Figure 28.—Apparatus which was developed in 1929 by the Gulf Research and Develop- ment Company, Harmarville, Pennsylvania. It was designed to achieve an accuracy within one ten-millionth of the true value of gravity, and represents the extreme develop- ment of pendulum apparatus for relative gravity measurement. The pendulum was designed so that the period would be a minimum. The case (the top is missing in this photograph) is dehumidified and its temperature and electrostatic condition are controlled. Specially designed pendulum-lift
. Bulletin - United States National Museum. Science. w If. Figure 28.—Apparatus which was developed in 1929 by the Gulf Research and Develop- ment Company, Harmarville, Pennsylvania. It was designed to achieve an accuracy within one ten-millionth of the true value of gravity, and represents the extreme develop- ment of pendulum apparatus for relative gravity measurement. The pendulum was designed so that the period would be a minimum. The case (the top is missing in this photograph) is dehumidified and its temperature and electrostatic condition are controlled. Specially designed pendulum-lifting and -starting mechanisms are used. The problem of flexure of the case is overcome by the Faye-Peirce method (see text) in which two dynamically matched pendulums are swung simultaneously, 1800 apart in phase. the action of one pendulum upon a second pendulum hung on the same stand. This method of determining the correction for flexure was a development from a "Wippverfahren" invented at the Geodetic Institute in Potsdam. A dynamometer was used to impart periodic impulses to the stand, and the effect was observed upon a pendulum initially at rest. Refine- ments of this method led to the development of a method used by Lorenzoni in 1885-1886 to determine the flexure of the stand by action of an auxiliary 336 pendulum upon the principal pendulum. Dr. Schu- mann, in 1899, gave a mathematical theory of such determinations,88 and in his paper cited the mathemat- ical methods of Peirce and Cellerier for the theory of Faye's proposal at Stuttgart in 1877 to swing two similar pendulums on the same support with equal amplitudes and in opposite phases. "" Dr. R. Schumann, "Uber die Vervvendung zweier Pendcl auf gemeinsamcr Unterlage zur Bestimmung der Mitschwin- gung," Zeitschrijt fur Mathematik und Physik (1899), vol. 44, p. 44. BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY. Please note that these images are extracted from scann
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