Astronomical Society. 443 



and 5 feet focal length, with a power of 100. It appeared in contact 

 at about half-past 10, by inference, and for some minutes remained 

 on the edge of the hmb, presenting an appearance not unlike that 

 of the lunar mountains coming into view during the first quarter of 

 the moon, until it finally disappeared on the body of the planet. 

 At least twelve or thirteen minutes must have elapsed, when, acci- 

 dentally turning to Jupiter again, to my astonishment I perceived 

 the same satellite outside the disc! It was in the same position as 

 to being in a line with the apparent lower belt, where it remained 

 distinctly visible for at least four minutes, and then suddenly va- 

 nished." 



The same phsenomenon was also observed on the same evening, 

 at different places, by Mr. Maclear and Dr. Pearson. 



II. A letter from" Mr. Dawes to Mr. Herschel, giving observa- 

 tions of the double stars, 70 Ophiuchi, g Ursae Majoris, 44- Bootis, 

 7 Virginis, y; and <r Coronae, Castor, y Leonis, and s Bootis, made 

 during the last and present year. Mr. Dawes is of opinion that the 

 apparent discs are more affected by the aperture of the telescope 

 than by any other circumstance; and that this is the principal 

 reason why a reflector presents a smaller image of a fixed star than 

 an achromatic of equal illuminating power. 



III. The reading of Mr. Herschel's paper on the measures of 

 364 double stars was completed. 



This paper contains the raicrometrical measures of the angles 

 of position and distances of 364 double stars, observed by Mr. Her- 

 schel with the seven-feet equatorial in his possession at Slough, the 

 same which was used by Sir James South in his observations at 

 Passy, and in a part of the measures of double stars in the Philoso- 

 phical Transactions for 1824. The individual measures, being too 

 numerous, are not stated; but the mean results of each night's ob- 

 servation are set down in tabular order, with a weight attributed to 

 each, indicative of the degree of confidence which the observer him- 

 self attributes to them, and with notes attached, descriptive of any 

 peculiar circumstances in the observation proper to be recorded. 

 They comprise the results of 735 sets of measures, or from 6000 to 

 8000 individual observations, obtained under all atmospheric cir- 

 cumstances, in the years 1828, 1829, and 1830. Almost all the 

 stars observed are taken from the great catalogue of Struve. 



The author prefaces his observations by a comparison of his 

 results with those already obtained by other observers in the cases 

 where his stars have been ob.served by others, and draws a conclu- 

 sion not unfavourable to the general accuracy of his angles of posi- 

 tion ; although, in some individual cases, considerable discrepancies 

 and even grievous errors are admitted. In the course of this com- 

 parison he is led to point out some stars as having so materially 

 changed, at least apparently, thai ho is induced to recommend them 

 for further observation, as being possibly of a binary nature. With 

 regard to his distances, he professes himself much dissatisfied, owing 

 to an imperfection in the micrometer attached to the instrument, 

 3 L 2 whioh 



