Figure 10. Henry Kater 11777- 

 [835) I nglish army offii ei and 

 phj ni ist. 1 [is 31 ientift 

 gan during his militarj service in 

 Inili.i. where he assisted in the 

 "great tri in ey." 



Returned to En ise ol 



bad health, and retired in ifii p he 

 pioneered < 1818) in the develop- 

 ment of the convertible pendulum 

 .is .in alternative to the approxima- 

 tion ni the "simple" pendulum foi 

 the measurement of tin- "se< onds 

 pendulum." Kater's convertible 

 pendulum and the invai iable pen- 

 dulum introduced l>\ him in 1819 

 wen- the basis of] ngli h pi ndulum 

 work. [Photo courtesy National Por- 

 trait Gallery, London.) 



pendulum was carried out by Borda and Cassini by 

 methods previously described. Bohnenberger in his 

 me 1 1 slii,-" made the proposal to employ a 

 convertible pendulum for the absolute determination 

 ni gravit) : thus, he lias received credit for priority in 

 publication. Capt. Kater independently conceived 

 ni the convertible pendulum and was the first to 

 design, construct, and swing one. 



After his observations with the convertible pendu- 

 lum, Capt. Kater designed an invariable compound 

 pendulum with a single knife edge but otherwise simi- 

 lar in external form to the convertible pendulum"' 

 (fig. 1 ii. Thirteen of these Kater invariable pendu- 

 lums have been reported as constructed and swung 

 al stations throughout the world. * a Kater himself 

 swung an invariable pendulum at a station in London 

 and at various other stations in the British Isles. 

 Capt. Edward Sabine, between 1820 and 1825, made 

 voyages and swung Kater invariable pendulums at 

 stations from the West Indies to Greenland and 



2> Collection de memoir es, vol. 4, p. B-74. 



n Phil. Trans. (1819), vol. 109, p. 337. 



MJOHN Herschel, "Notes for a History of the Use of 

 [nvariable Pendulums," The Great Trigonometrical Suney of India 

 (Calcutta, 1879), vol. 5. 



Figure I I . 1 111 Mil Mil Hi VPPROX1MATI 



the simple pendulum in 



gravity experiments ended in 

 when Henry [Cater invented the com- 

 pound 1 onvertible pendulum, from whit h 

 the equivalent simple pendulum could be 

 obtained according to the method ol 

 Huygens (see text, p. 314). Developed in 

 1 linn with a project to li\ ih<- 

 standard ol English measure, Kater's pen- 

 dulum was called "compound" because it 

 was .1 solid bar rather than the fine wire 

 or string wit 1 1 which earlier experimenters 

 had tried to approximate a "weightless" 

 rod. It was called convertible l>< 

 is alternately swung from the two knife 

 1 and l>) at opp site ends I he 

 weights (/and g) are adjusted so that 1 If 

 period of the pendulum is the same from 

 either knife edge, ["he distance between 

 the two knife edges is then equal to the 

 length of the equivalent simple pendulum. 



PAPER 44: DEVELOPMENT OF GRAVITY PENDULUMS IN THE 1 9TH CENTURY 



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