[79] The stations at which observations were conducted with the Peirce pendulums are recorded in the reports of the Superintendent of the U.S. Coast and Geodetic Survey from 1881 to 1890. [80] _Comptes-rendus de l'Académie des Sciences_ (Paris, 1880), vol. 90, p. 1401. HERVÉ FAYE's report, dated June 21, 1880, is in the same _Comptes-rendus_, p. 1463. [81] COMMANDANT C. DEFFORGES, "Sur l'Intensité absolue de la pesanteur," _Journal de Physique_ (1888), vol. 17, pp. 239, 347, 455. See also, DEFFORGES, "Observations du pendule," _Mémorial du Dépôt général de la Guerre_ (Paris, 1894), vol. 15. In the latter work, Defforges described a pendulum "reversible inversable," which he declared to be truly invariable and therefore appropriate for relative determinations. The knives remained fixed to the pendulums, and the effect of interchanging knives was obtained by interchanging weights within the pendulum tube. [82] Papers by MAJ. VON STERNECK in _Mitteilungen des K. u. K. Militär-geographischen Instituts, Wien_, 1882-87; see, in particular, vol. 7 (1887). [83] T. C. MENDENHALL, "Determinations of Gravity with the New Half-Second Pendulum...," _Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1890-91_ (Washington, 1892), part 2, pp. 503-564. [84] W. H. BURGER, "The Measurement of the Flexure of Pendulum Supports with the Interferometer," _Report of the Superintendent of the U.S. Coast and Geodetic Survey for 1909-10_ (Washington, 1911), app. no. 6. [85] E. J. BROWN, _A Determination of the Relative Values of Gravity at Potsdam and Washington_ (Special Publication No. 204, U.S. Coast and Geodetic Survey; Washington, 1936). [86] M. HAID, "Neues Pendelstativ," _Zeitschrift für Instrumentenkunde_ (July 1896), vol. 16, p. 193. [87] DR. R. SCHUMANN, "Über eine Methode, das Mitschwingen bei relativen Schweremessungen zu bestimmen," _Zeitschrift für Instrumentenkunde_ (January 1897), vol. 17, p. 7. The design for the stand is similar to that of Peirce's of 1879. [88] DR. R. SCHUMANN, "Über die Verwendung zweier Pendel auf gemeinsamer Unterlage zur Bestimmung der Mitschwingung," _Zeitschrift für Mathematik und Physik_ (1899), vol. 44, p. 44.