MADE AT LANCASTER. 115 



April 5th. Emersion of the 2d satellite of Jupiter, observed 

 at 10" 23' 29" mean time, or 10 h 20' 41" apparent time: — 

 night very clear and the belts distinct: — magnifying power 

 100. 



9th. Emersion of the 1st satellite of Jupiter, observed at 

 9 h 9' 59" mean time, or 9 h 8' 20" apparent time: — night 

 clear, and belts distinct: — magnifying power 100. 



22d. Immersion of the 4th satellite of Jupiter, observed at 

 12 h 4]' 19" mean time, or 12 h 42' 54" apparent time. At 

 the time this observation was made, the night was very serene 

 and clear: — four belts were distinctly defined on the body of 

 the planet: — magnifying power 100. 



Emersion of the above satellite was observed at 14 h 52' 34" 

 mean time, or 14 h 54' 10" apparent time. — The night had 

 become a little hazy, and the belts were scarcely discernable. 

 — The satellite appeared for a few seconds, and then became in- 

 visible for more than a minute. From the state of the atmos- 

 phere, and the slow manner in which the satellite acquired its 

 light, owing to its oblique way through the shadow of Jupiter, 

 it is my opinion, that at least 2 minutes should be deducted 

 from the observed time of the emersion; which deduction I 

 shall accordingly use in making out the result of the observa- 

 tion. 



May 2d. Emersion of the 1st satellite of Jupiter, observed 

 at 9 h 21' 34" mean time, or 9 h 24' 46" apparent time: — 

 night clear, and belts distinct: — magnifying power 100. 



9th. Emersion of the 4th satellite of Jupiter, observed at 

 8h 39' 2S" mean time, or 8 h 43' 17" apparent time. — The 

 planet and satellites were well defined, and the observation one 

 of the most satisfactory I have made at this place : — magnify- 

 ing power 100. 



Emersion of the 1st satellite of Jupiter, observed at 1 in 15' 

 46" mean time, or 1 l h 19' 35" apparent time. This eve- 

 ning I began to pay attention to the decrease of Saturn's 

 ring. 



emersions dont on puissc ctre bien assure; car quand 1' etoile sort de la partie c clairec de la lime, sa 

 lumiere, trop foible par rapport a celle de la lune, ne se distingue pas facilement aupremierin- 

 stant del' emersion. 



Astronomie par la Lande art. 1990. 



