222 Mr. South on the Eclipses of [March, 



" Prior to taking the transit of Aldebaran, the five feet equa- 

 torial was placed upon Jupiter, and immediately after the transit 

 had been secured, I went to see how matters were going on ; the 

 fourth satellite was at this time about the splendour of a star of 

 the ninth magnitude, and of a light blue colour. The night was 

 remarkably clear ; I determined to remain at the instrument as 

 long as the satellite continued visible, which, according to the 

 Nautical, would be at least a quarter of an hour. To make my- 

 self comfortable, therefore, I placed some blocks of wood upon 

 the double steps, and took my seat very quietly : the lights, 

 except that at the clock, were all put out ; it continued diminish- 

 ing in lustre till 4 h 34' 57" per clock, at which time I could see it 

 no more. I observed it of the brightness of the small star near 

 a. Lyrae for more than a minute. 



" Emersion of the fourth satellite (observatory darkened as 

 before) at 6" 43' 5" per clock. 



" At 6 h 45' about as bright as the pole star. 



" At 6 h 52' had not half the splendour of the dullest of the 

 other three which were visible. Unable to spare more time, 

 further observation was given up." 



Greatly satisfied with my own observations, I was in hopes 

 that the extraordinary fineness of the night would have rendered 

 correspondent ones, at various stations, almost certain ; but in 

 this I have had the mortification to find myself disappointed. 

 The only observer who, as far as I have ascertained (and I have 

 made very extensive inquiry), was similarly engaged with myself, 

 is to be found in Col. Beaufoy : it is however indeed fortunate 

 that it was he. My opinion of his observations of the eclipses 

 of Jupiter's satellites, has long been before the public ; so that 

 I cannot now be suspected of commending his accuracy, merely 

 to suit my present purpose. 



My observations made with the five feet equatorial, the object 

 glass of its telescope has 64 inches focus, and 3f inches clear 

 aperture; power 133. 



Gol. Beaufoy's telescope has an object glass, precisely of the 

 same diameter, but of 56*5 inches focal length : it is mounted 

 on a very steady stand, but not equatorially. Magnifying power 

 used = 86. 



Prior to observation, he excluded all light from his observatory, 

 except what was sufficient to enable him to distinguish the hands 

 of his clock. 



Longitude of Blackman-street observatory . . . = 0' 21-76" W. 



Bushey = 1 20-93 W. 



Diff. of long. Bushey to the W = 59-17 



Blackman-street Observations. Bushey Observations. 



Immersion 4" 35' 3-89" Immersion 4 h 32' 27-09" 



Emersion 6 43 11-89 Emersion 6 43 50-46 



(Sidereal time at each station.) 



