OF ARTS AND SCIENCES. 327 



Three hundred and seventh Meeting. 



April 4, 1848. — Monthly Meeting. 



The President in the chair. 



Mr. Bond communicated a farther notice respecting the 

 third satellite of Jupiter, as follows : — 



" In my communication of the 5th of February, I gave some ac- 

 count of a remarkable change which took place in the appearance of 

 the third satellite of Jupiter, while transiting his disk on the evening of 

 January 28th. I am now enabled, from subsequent observation, to 

 confirm in a more detailed manner the account then given. 



"During the evening of March 11th, this satellite was again seen as 

 a Hack spot upon the disk of the primary ; but as several visitors were 

 present at the Observatory, the observations were discontinued. It 

 was remarked, however, that the spot was of less magnitude than the 

 shadow which subsequently passed the disk. 



" On the 18th of March, we were more fortunate. The state of the 

 atmosphere proving favorable, I watched, with my son, the entire tran- 

 sit. The following are the results of our observations. 



" At 8''' 15™' sidereal time of the Observatory, we commenced, by 

 estimating independently the relative order of brightness of the sat- 

 ellites ; it was, — first, third, second, fourth. 



" The third satellite, when close to the limb of Jupiter, suffered no 

 diminution of its brightness or apparent magnitude. 



"At the first contact with the primary, the latter seemed to recede 

 from the satellite. 



" At S*"- SI""-, the contact of the centre of the satellite with the limb 

 of Jupiter took place. 



" S*"' 55™-. First internal contact; the satellite was then seen dis- 

 tinctly on the disk, brighter than Jupiter, although it had entered on a 

 bright channel between the great belt and a smaller one south of it. 

 The satellite was'thought to be less bright on its southern limb. 



"At 9''' 15™-, it had decreased in brightness so as to become hardly 

 perceptible. 



" At 9^' 18™' 15'', my son, who was now observing, exclaimed quick- 

 ly, — ' The dark spot is coming on ; I now see the satellite ; the dark 

 spot is on the right hand, perhaps a little above ! ' On examination, I 

 found the spot was quite distinct. 



