Drawing of pendulum experiment to determine the length of the seconds pendulum at Paris, conducted in 1792 by <a href="https://en.wikipedia.org/wiki/Jean-Charles_de_Borda" class="extiw" title="wikipedia:Jean-Charles de Borda">Jean-Charles de Borda</a> and <a href="https://en.wikipedia.org/wiki/Jean-Dominique_Cassini" class="extiw" title="wikipedia:Jean-Dominique Cassini">Jean-Dominique Cassini</a>.  From their original paper.  They used a pendulum that consisted of a 1 1/2 inch (3.8 cm) platinum ball suspended by a 12 foot (3.97 m) iron wire <i>(F,Q)</i>. It was suspended in front of the pendulum <i>(B)</i> of a precision clock <i>(A)</i>.  Alterations to image: moved observer <i>(O)</i> closer to wall to reduce unwieldy size of image, converted to PNG. Image shows aliasing artifacts (crosshatching) from scanning of original halftone image.
Jean-Charles de Borda and Jean-Dominique Cassini
Downloaded <a href="//commons.wikimedia.org/w/index.php?title=2009-01-27&amp;action=edit&amp;redlink=1" class="new" title="2009-01-27 (page does not exist)">2009-01-27</a> from <a rel="nofollow" class="external text" href="https://books.google.com/books?id=A1IqAAAAMAAJ&amp;pg=RA2-PA317">Victor F. Lenzen, Robert P. Multauf (1964) 'Paper 44: Development of gravity pendulums in the 19th century' in <i>United States National Museum Bulletin 240: Contributions from the Museum of History and Technology</i>, reprinted in <i>Bulletin of the Smithsonian Institution</i>, 1964, Smithsonian Institution Press, USA, p.317, fig.13</a> on Google Books.  Image credited in text to  J. C. Borda and J. D. Cassini de Thury, 'Experiénces pour connaitre la longuer de pendule qui bat les secondes à Paris', in <i>Collection de Mémoires Relatifs a la Physique, publiés par la Société Française de Physique</i>, Vol.4, <i>Mémoires sur le pedule, précédés d'une bibliographie</i>, Gauthier-Villars, Paris, 1889, Plate 2.