118 ASTRONOMICAL OBSERVATION'S 



h I li h 1 11 



19th. Immer. 3d sat. 5 5 27 5 13 55 



too great 23 too great 8 51 



29th. Emer. 2d sat. . . 5 5 20 5 5 42 



too great 16 too great 38 



April 5th. Emer. 2d sat. 5 5 22 5 5 40 



too great 18 too great 36 



9th. Emer. 1st sat. 55 4 5 5 40 



too great too great 36 



22d. Immer 4th sat*. 5 3 28 4 44 30 



too small 1 36 too small 20 34 



do. Emer. do. 5 4 16 5 6 55 



too small 48 too great 1 51 



May 2d. Emer. 1st sat. 5 5 1 55 38 



too small 3 too great 34 



9th. Emer. 4th sat. 5 6 26 5 11 23 



too great. ... 1 22 too greai 6 19 



do. 1st sat, 55 16 : 564 



too great. ..;... 12 too great 10 



14th. Emer. 2d sat. 5 5 30 5 5 38 



too great 26 too great 34 



June 13th. Immer. 3d sat. 5 4 41 5 13 1 



too small 23 too great 7 57 



17th. Emer. 1st sat. 5 5 9 : 5 5 58 



too great 5 too great 54 



On the 23d of February the pendulum with a wooden rod 

 was taken from the clock and replaced by a grid-iron one; 

 but, owing to the unfavourable situation of the clock, I did 

 not expect to derive any material advantage from the change; 

 in this however I have been agreeably disappointed; the ex- 

 treme variations from the mean rate of going for the whole 

 year, will not amount to 2 seconds, notwithstanding the con- 



* The theory of the 4th satellite of Jupiter is a subject of peculiar nicety, and has required great 

 labour to bring it to its present degree of perfection ; for which we are principally indebted to the 

 genius, and industry of Mr. Delambre. An error so small in the inclination of the orbit of this 

 planet, or in the place of the nodes, as to be scarcely distinguished from the unavoidable errors of 

 observation, when the satellite passes through the center of Jupiter's shadow, will become very 

 considerable as it is leaving it at either pole j because, those errors increase nearly in the ratio of 

 the squares of the satellite's distances from the centerof the shadow. From the immersion, and 

 emersion of April 22d, to which this note refers, it appears, that the inclination of the orbit of this 

 satellite, is either stated too small in the theory used by the computers of the British nautical alma- 

 nac, or is subject to changes not yet introduced into these tables. 



