1869.] Corrections to Pendulum Observations. 



491 



the four months during which the experiments were carried on, each re- 

 sult being of course employed for the pendulum-experiments of the corre- 

 sponding day. The Table shows that our plan was the safest, as differences 

 of nearly one second are observable ; these differences have, however, ap- 

 parently no connexion with changes of temperature, as the rate of the clock 

 during the artificial heating of the pendulum-room, of which we shall soon 

 have to speak, showed hardly any difference from the mean rate, proving 

 that the compensation was not faulty. 



The pendulum-clock showing sidereal time, the Table is calculated 

 from the formula: — Number of vibrations in a mean solar day =N' = 



86636*5554^1 — g^j^^ ; and hence: Number of vibrations of detached 



VN' 



pendulum =N=-yr, where V, V are respectively the number of vibra- 

 tions of the detached and clock-pendulum from beginning to the end of 

 our experiment. 



Table I. Number of Vibrations made by the clock-pendulum during a 

 mean solar day. 



1866. 



September. 



October. 



November. 



December. 





76577-40 



86577-38 



86577-43 



86577-50 



2. 



'3i 



•25 



•32 



•40 



3- 



•50 



■14 



•20 



'39 



4- 



•29 



•09 



86576-99 



•48 



5- 



86576-97 



•21 



86577-02 



'3 1 



6. 



•83 



•22 



86576-94 



'39 



7- 



•81 



•06 



'95 



•50 



8. 



•88 



86576-91 



'99 



'54 



9- 



•90 



86577-00 



86577-11 



'54 



IO. 



86577-04 



•11 



•17 



•51 



ii. 



•00 



•13 



•24 



•61 



12. 



•07 



•28 



'33 



•68 



13- 



•26 



•10 



•28 



•70 



14. 



•16 



•04 



•40 



•70 



15- 



•11 



•22 



•53 



•64 



16. 



•08 



•29 



•61 



•64 



17. 



86576-98 



■40 



•60 



•60 



18. 



•90 



•50 



•70 



•70 



19. 



•70 



■54 



75 



•71 



20. 



•90 



•60 



71 



•66 



21. 



'99 



•61 



•80 



'59 



22. 



•93 



•43 



"74 



•40 



23- 



•85 



•28 



•70 



'47 



24. 



•83 



•27 



•62 



'44 



25. 



*99 



'47 



•51 



•46 



26. 



86577*20 



•40 



•49 



•48 



27. 



-21 



•29 



•44 



'47 



28. 



•33 



•33 



•64 



•59 



29. 



•30 



•35 



•56 



•61 



3°- 



86577-24 



•29 



86577*56 



'5 1 



3i. 



86577-40 





86577-56 



C. Correction for temperature, — The method of suspending the ther- 



