OF THE VIBRATIONS OF AN INVARIABLE PENDULUM. 



235 



Whence the vibrations within the receivers are in this experiment in defect, 

 0.21 per diem. 



Collecting the three results in one view, they are as follows : 

 Feb. 17- Exp. IX. The vibrations within the glasses in excess 0.34 

 Feb. 21. Exp. X. The vibrations within the glasses in defect 0.15 

 Feb. 22. Exp. XI. The vibrations within the glasses in defect 0.21 



Mean. The vibrations within the glasses in defect 0.007 per diem. 



We may therefore conclude that the vibration in air within the glasses, and 

 in the free air of the apartment, the glasses being removed, will lead by suffi- 

 cient repetition to an identical result. 



Finally, the knife edge being examined, was found apparently as clean and 

 sharp as when first used. The agate planes had retained their horizontality ; 

 and the screws securing the planes to the circular plate, and the plate to the 

 iron frame, were as tight as when the experiments were commenced. 



We have now to collect in one view the several results, from whence the re- 

 duction to a vacuum for an invariable pendulum vibrating in air is to be de- 

 rived. 



London . . 

 London . . 

 Greenwich 

 Greenwich 

 Greenwich 

 Greenwich 

 Greenwich 

 Greenwich 



7.38 



9.065 



9.54 



9.17 



10.38 



5.705 



10.525 



10.560 



Mean 9.042 



2 h2 



26.197 



72.01 

 69.70 

 35.89 

 32.37 

 36.40 

 35.65 

 38.10 

 41.25 



45.17 



