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, 180 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 



