United States Coast and Geodetic Survey

Abstract

THIS appendix is a portion of the Annual Report of the U.S. Survey, and contains the pendulum observations made in 1879-1880 by Mr. C. S. Peirce at three stations in Pennsylvania-namely, at the Alleghany Observatory, at Ebensburg, and at York. The observations form part of a series undertaken in connection with the Geodetic Survey of the United States. A Repsold reversible pendulum was used and oscillated in vacua, using various kinds of supports. At York a series of experiments were made to determine the effect of the flexure of the support. It appears from a previous report (Appendix No. 14 of 1881) that Mr. C. S. Peirce maintained against MM. Plantamour and Hirsch in Switzerland, that the oscillations of the support have a marked effect on the time of oscillation of the pendulum, and he accordingly undertook an exhaustive series of experiments to prove his point, and to measure the allowance to be made. The experiments given in Appendix No. 19 are only a small portion, and are in fact re-published from Appendix No. 14, with some few corrections. The question was disposed of in Appendix No. 14, and it was clearly shown that the flexure of the support ought to be taken into account, and it is evident, therefore, that the stiffness of the support is of vital importance. Experiments were also made at York to determine the relative value of the method of transits and a method of eye and ear coincidences invented by Mr. Farquhar; the method is not described, but appears to be far less accurate than the method of transits. The effect of substituting steel cylinders for the usual knives was also tried, and every care taken to prevent the inclusion of dust, but the results were very unsatisfactory.

United States Coast and Geodetic Survey.

Determination of Gravity at Stations in Pennsylvania, 1879–1880. Appendix No. 19. Report for 1883.