+42 Astronomical Society. 



ASTRONOMICAL SOCIETY. 



June 10. — The following communications were read : — 

 I. Observed occultation of Jupiter and his satellites by the moon, 

 June 1,1 831. 



1. By the Astronomer Royal, giving the contact, immersion of 

 Jupiter's centre, and total immersion, by four observers; and the 

 emersions of Jupiter and the four satellites, by seven observers. 



2. By Rlr. Snow, containing the complete observations of all the 

 immersions and emersions, made in Savile Row, together with the 

 observed transits by which the clock error was determined. 



JNIr. Snow observes : 



" Between the contact of the moon's limb with the planet, and 

 the planet's disappearance, 1' 32" elapsed ; and during that time 

 no change of light, colour, or motion, took place in the planet, 

 %vhich remained uniformly of a rather more dusky colour than the 

 moon. Both the planet and moon were in a violent state of undu- 

 lation during the immersion ; but the moon's undulation was seen 

 quite distinctly upon the planet's disc, and differed, for that small 

 arc, in no respect from tiie undulation of the rest of the limb. I 

 watched very particularly for any projection of the planet upon the 

 moon's edge, but could see none. 



" It is perhaps worth mentioning, that the planet's second limb, 

 during, and for several seconds after its final emersion, and in both 

 states of the adjustment of the telescope, appeared to have a very 

 considerable curvature towards the moon's dark limb. The planet, 

 however, soon returned to a shape nearly spheroidal." 



3. By Captain Smyth, containing the same observations. Captain 

 Smyth also remarks : 



"Although the emersions of the satellites were perfectly distinct, 

 they were certainly not so instantaneous as those of the small stars; 

 which I think was more owing to light than disc. Jupiter entered 

 into contact rather sluggishly; but though the lunar limb was 

 tremulous from haze, there was not the slightest loss of light. 

 Faint scintillating rays preceded the emersion, which was so gra- 

 dual, that, as the planet re-appeared, the edge of the moon covered 

 it with a perfectly even and black segment, which cut the belts 

 distinctly, and formed clear sharp cusps, slowly altering until the 

 whole body was clear. There was no appearance of raggedness 

 from lunar mountains, and Jupiter's belts were superbly plain while 

 emerging ; but there was not the slightest distortion of figure, 

 diminution of light, or change of colour." 



In allusion to the deviation seen by Messrs. Ross and Comfield, 

 which is inserted in the Memoirs, Captain Smyth mentions the 

 following fact : 



" On Thursday the 26th of June, 1828, the moon being nearly 

 full, and the evening extremely fine, I was watching the second 

 satellite of Jupiter as it gradually approached to transit its disc. 

 My instrument was an excellent refractor, of iJf inches aperture, 



and 



