liG Royal Astronomical Society. 



for the widening of the separation, and that in a greater degree towards 

 the sides which are more remote from the circumference." 



The author then proceeds to illustrate his explanation by means 

 of diagrams applying to the different phases of the phaenomenon ; 

 and he considers the principles laid down in explanation to possess 

 the character of a vera causa, though they may not suffice to ex- 

 plain all the phsenomena. 



Differences in the appearances of the beads as described by differ- 

 ent observers must also be expected, both from the preceding theory, 

 and from the circumstance that there are differences in the power 

 and aperture of the telescopes employed. The author hopes shortly 

 to be able to offer to the Society some contributions towards the 

 better elucidation of this subject. 



It is perhaps questionable whether the same principles will afford 

 an explanation of certain apparently analogous phajnomena observed 

 in the transits of Venus ; but, in general, the adherence of the planet 

 to the limb of the sun by a neck at the point of junction, and the 

 protuberance of the disc towards the same part of the separation, 

 are appearances which agree sufficiently with the cause above as- 

 signed. 



In a note appended to Professor Powell's paper, he alludes to the 

 observations of the eclipse of October 9 of the present year, in which 

 small beads were observed, with waving in the limb, but without 

 increase or elongations of the shadows into threads, or any other 

 change. In the case of M. Schaub's observations, the complemen- 

 tary combination employed might, by the loss of light, have destroyed 

 any effects of irradiation. Also, as the ring formed was very thin, 

 the difference of the intensities of the sun's light for the breadth of 

 the band would be very small ; and thus the causes above referred to 

 might not act to a perceptible extent : the whole of the phsenomena 

 might be simply accounted for, as M. Mauvais observes, by the mere 

 consideration of the irregularities of the moon's limb as it just 

 touched that of the sun. 



Results deduced from the Occultations of Stars and Planets by 

 the Moon, observed at Cambridge Observatory from 1830 to 1835. 

 By the Astronomer Royal. 



These occultations were reduced at the time in the most complete 

 manner which was then practicable. A very approximate place of 

 the star having been assumed, the apparent place of the point of the 

 moon's limb at which the occultation took place was known, and by 

 the application of the proper correction for parallax, the geocentric 

 place of the same point for the instant of occultation was also known. 

 The geocentric place of the moon's centre was computed for the in- 

 stant of occultation, according to the lunar tables. From the sphe- 

 rical coordinates of these two points, their distance was computed, 

 which ought to be equal to the tabular semidiameter of the moon. 

 Any discordance must arise from some of the following sources : — 

 an error in the assumed R.A. or N.P.D. of the star, an error in the 

 tabular R. A. or N.P.D. of the moon, an error in her parallax or semi- 

 diameter, or in the time of observation. The effects of errors of all these 



