THERMOMETRICAL OBSERVATIONS. 237 



Equal altitudes of the Sun on that day. 



A. M. 8 47 50. P. M. 3 



12 



Add 



Dedu(S forenoon's obfervation 



Half . . . . 

 Add the forenoon's obfervation 



Dedudl for change of the 0's declination 



O's centre pafled the meiiJiau bj c4Uiil altitudes at 



Which differs from the obfcrved time but T'^ths of a fecond. 



The paffage of the Rars over the meridian afford an eafy, and accurate 

 method of determining the rate of the going of a clock, as is well known 

 to all aftronomers ; and when the right afcenfion of a ftar is well fettled, 

 die error of a clock can be determined by it with great precilion, — as for 

 example, take the paffage of Sirius on the 27th of March. 



h t II 



Right afcenfion of Sirius the beginning of 1800 accord- 1 ^ ^ 



ing to De Zach* j" ^ ^^ '9-5 



Dedudt ann. preceffion for one year . . . . — 2.6 



Right afcenfion the beginning of 1 799 

 Aberration and preceflion on the 27th of March 

 Nutation . do. .... 



True right afcenfion of Sirius 

 )'s right afcenfion by the Na 

 Sirius palfed the meridian, dedud 



©'s right afcenfion by the Nautical Almanac at the time! 



Siiius palfed the meridian apparent time at 

 Do. . . by obfervation 



Clock too flow apparent time ..... 



Vol. V. I i O's centre 



* Vide Obfervationibus Aflronomicis Annis 1787, 1788, 1789, 1790. 



