OP A PENDULUM AT GREENWICH AND LONDON. 



;kr« 



^ 



vibrations at 62°, the temperature of the air being 71°-^, the barometer 29.533, 

 and the mercury 32°. The reduction to a vacuum is + 9-63, making 85969.34 

 vibrations at 62°. hi*' 



The second series at Greenwich was commenced on the 21st of July, and 

 continued to the 26th, both days included. The clock and thermometer em- 

 ployed were the sanie as on the former occasion ; the rate of the clock was sup- 

 plied by Mr. Thomas Glanville Taylor, by comparison with the transit clock of 

 the observatoiy, as shown in the memorandum E. The experiments are given 

 at length in the Table F, and their results collected in one view are as follows. 



Greenwich, July 1828 ; Experiments with Pendulum 12. 



Barom. Therm. Vibrations at 62*. 



61.49 85960.16 



60.17 85959.70 



61.45 85959.89 



61.93 85969.82 



62.24 85960.04 



61.63 85960.15 



61.5 



85959.96 



The height of the barometer corrected for capillary action and reduced to 

 32° is 29.446. 



The mean result is 85959.96 vibrations in a mean solar day at 62° ; the 

 temperature of the air being 61.5, the barometer 29.446, and the mercury 32°. 

 The reduction to a vacuum is + 9.82, making 85969.78 vibrations at 62°. 



We have thus a second series of the vibrations of Pendulum 12 at London 

 and Greenwich, after its knife edge had been ground and figured afresh, as 

 follows. 



London 85969.34 



Greenwich. . . . 85969.78 



Difference 



0.44 



Showing an acceleration at Greenwich of 0.44 of a vibration per diem. The 

 former result was an acceleration of 0.52 of a vibration per diem. We may 

 therefore assume finally, 0.48 of a vibration per diem as the difference in 



