Figure 12. — I hi-: Kater convertible pendulum in use is placed before a clock, whose 

 pendulum bob is directly behind the extended "tail" of the Kater pendulum. A white 

 spot is painted on the center of the bob of the clock pendulum. The observing telescope, 

 left, has a diaphragm with a vertical slit of such width that its view is just filled by the tail 

 of the Kater pendulum when it is at rest. When the two pendulums are swinging, the 

 white spot on the clock pendulum can be seen on each swing except that in which the two 

 pendulums are in coincidence: thus, the coincidences are determined. (Portion of plate 

 5, Memoires publics par la Sociele franqaise de Physique, vol. 4.) 



Spitzbcrgen. 29 In 1820, Kater swung a Kater invari- 

 able pendulum at London and then sent it to Golding- 

 ham, who swung it in 1821 at Madras, India. 30 Also 

 in 182H, Kater supplied an invariable pendulum to 

 Hall, who swung it at London and then made observa- 



!e Capt. Edward Sabine, "An Account oi Experiments to 

 Determine the Figure of the Earth," Phil. Trans. (1828), vol. 118, 

 p. 76. 



30 John Goldingham, "Observations for Ascertaining the 

 Length of the Pendulum at Madras in the East Indies." Phil. 

 Trans. (1822), vol. 112, p. 127. 



tions near the equator and in the Southern Hemi- 

 sphere, and at London again in 1823. 31 The same 

 pendulum, after its knives were reground, was de- 

 livered to Adm. Liitke of Russia, who observed 

 gravity with it on a trip around the world between 

 1826 and 1829. 32 



31 Basil Hall, "Letter to Captain Kater Communicating 

 the Details of Experiments made by him and Mr. Henry 

 Foster with an Invariable Pendulum." Phil. Trans. (1823), 

 vol. 113, p. 211. 



32 See Collection de memoires, vol. 4, p. B-103. 



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BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



