held from the 15th to the 22d of October 1864 in 

 Berlin. 50 The Conference decided upon questions 

 of organization : a general conference was to be held 

 ordinarily every three years; a permanent commission 

 initially consisting of seven members was to be the 

 scientific organ of the association and to meet annu- 

 ally; a central bureau was to be established for the 

 reception, publication, and distribution of reports 

 from the member states. 



Under the topic '"Astronomical Questions," the 

 General Conference of 1864 resolved that there 

 should be determinations of the intensity of gravity 

 at the greatest possible number of points of the 

 geodetic network, and recommended the reversible 

 pendulum as the instrument of observation. 51 At the 

 second General Conference, in Berlin in 1867, on the 

 basis of favorable reports by Dr. Hirsch, director of 

 the observatory at Neuchatel, of Swiss practice with 

 the Repsold-Bessel reversible pendulum, this instru- 

 ment was specifically recommended for determina- 

 tions of gravity. 52 The title of the association was 

 changed to Die Europaische Gradmessung; in 1886, it 

 became Die Internationale Erdmessung, under which 

 title it continued until World War I. 



On April 1, 1866, the Central Bureau of Die Euro- 

 paische Gradmessung was opened in Berlin under the 

 presidency of Baeyer, and in 1868 there was founded 

 at Berlin, also under his presidency, the Royal 

 Prussian Geodetic Institute, which obtained regular 

 budgetary status on January 1, 1870. A reversible 

 pendulum for the Institute was ordered from A. 

 Repsold and Sons, and it was delivered in the spring 

 of 1869. The Prussian instrument was symmetrical 

 geometrically, as specified by Bessel, but different in 

 form from the Swiss and Russian pendulums. The 

 distance between the knife edges was 1 meter, and 

 the time of swing approximately 1 second. The 

 Prussian Repsold-Bessel pendulum was swung at 

 Leipzig and other stations in central Europe during 

 the years 1869-1870 by Dr. Albrecht under the 

 Jin (lion of Dr. Bruhns, director of the observatory 

 at Leipzig and chief of the astronomical section of the 

 Geodetic Institute. The results of these first observa- 



tions appeared in a publication of the Royal Prussian 

 Geodetic Institute in 1871. 53 



Results of observations with the Russian Repsold- 

 Bessel pendulums were published by the Imperial 

 Academy of Sciences. In 1872, Prof. Sawitsch 

 reported the work for western Europeans in "Les 

 variations de la pesanteur dans les provinces occiden- 

 tales de l'Empire russe." 48 In November 1873, the 

 Austrian Geodetic Commission received a Repsold- 

 Bessel reversible pendulum and on September 24, 

 1 874, Prof. Theodor von Oppolzer reported on obser- 

 vations at Vienna and other stations to the Fourth 

 General Conference of Die Europaische Gradmessung in 

 Dresden. 54 At the fourth session of the Conference, 

 on September 28, 1874, a Special Commission, 

 consisting of Baeyer, as chairman, and Bruhns, Hirsch, 

 Von Oppolzer, Peters, and Albrecht, was appointed 

 to consider (under Topic 3 of the program) : "Obser- 

 vations for the determination of the intensity of 

 gravity," the question, "Which Pendulum-apparatuses 

 are preferable for the determination of many points'" 



After the adoption of the Repsold-Bessel reversible 

 pendulum for gravity determinations in Europe, work 

 in the field was begun by the U.S. Coast Survey under 

 the superintendence' of Prof. Benjamin Peirce. There 

 is mention in reports of observations with pendulums 

 prior to Peirce's direction to his son Charles on Novem- 

 ber 30, 1872, "to take charge of the Pendulum Experi- 

 ments of the Coast Survey and to direct and inspect all 

 parties engaged in such experiments and as often 

 as circumstances will permit, to take the field with 

 a party . . . ." M Systematic and important gravity 

 work by the Survey was begun by Charles Sanders 



50 Comptes-rendus de la Conference Ceodesique Internationale 

 reunie a Berlin du 15-22 Octobre 786-1 (Neuchatel, 1865). 

 [bid pai till, subpart E. 



52 Bericht iiber die Verhandlungen der torn 30 September bii 7 

 October 1867 zu Berlin abgehaltenen allgemeinen Confirm der 

 Europaischen Gradmessung (Berlin, 1868). See report of fourth 

 session, October 3, 1867. 



53 C. Bruhns and Albrecht, "Bestimmung der Lange 

 des Secundenpendels in Bonn, Leiden und Mannheim," 

 Astronomische-Geoddtische Arbeiten im Jahre 1870 (Leipzig: Verof- 

 fentlichungen des Konigliche Preussischen Geodatischen 

 Instituts, 1871). 



54 Bericht iiber die Verhandlungen der vom 23 bis 28 September 

 Isj l in Dresden abgehaltenen vierten allgemeinen Conjerenz der 

 Europaischen Gradmessung (Berlin, 1875). See report of second 

 session, September 24, 1874. 



55 Carolyn Eisele, "Charles S. Peirce — Nineteenth-Century 

 Man of Science," Scripta Mathtmatica (1959), vol 24, p. 305. 

 For the account of the work of Peirce, the authors are greatly 

 indebted to this pioneer paper on Peirce's work on gravity. It 

 is worth noting that the history of pendulum work in North 

 America goes back to the celebrated Mason and Dixon, who 

 made observations of "the going rate of a clock" at "the forks 

 of the river Brandiwine in Pennsylvania," in 1766-67. These 

 observations were published in Phil. Trans. (1768), vol. 58, 

 pp. 32' I 235. 



322 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



