284 British Association for the Advancement of Science. 



mean R. A. and North Polar distance of the object for the begin- 

 ning of 1830, together with a description, in abbreviated language, 

 of its appearance and physical peculiarities, as to size, brightness, 

 condensation, &c. The observations of double stars in the second 

 catalogue, express the mean place for the epoch above named, — 

 the angle of position of the stars with the meridian, as micromet- 

 rically measured at the time of observation, — the estimated dis- 

 tance, and the magnitude assigned to each star, with a column 

 of remarks, in which are noted peculiarities of color, &c. 3. Mi- 

 crometrical Measures of 407 principal Double Stars of the South- 

 ern Hemisphere, made at the Cape of Good Hope, loith a 7 feet 

 Achromatic Equatorial Telescope. These measures were taken 

 with the same achromatic and micrometer, and are arranged in pre- 

 cisely the same manner as the former similar observations made 

 by Sir J., and printed in the Trans, of Royal Astron. Society. 

 Among the principal double stars in this paper occur, a Centauri, 

 « Crucis, 7 Centauri, 7 Lupi, i^ Lupi, n Lupi, ^ Hydrse, s Chamele- 

 ontis, 7 Piscis volantis, 7 Coronse Australis, «fcc. These measures 

 afford unequivocal evidence of rotation in some of these double 

 stars, particularly in a Centauri, ^ Hydras, 7 Coronas, and n Lupi. 

 In ct Centaviri, the decrease of distance, even within the short pe- 

 riod of observation, is remarkable ; and Sir J. remarked, that on 

 examining the catalogues of the Astron. Soc, and that of Capt. 

 Johnston, and the Paramatta Catalogue, in all which, the places 

 of the two stars are given separately, he finds this diminution of 

 distance fully borne out and regularly progressive ; from which 

 he concludes that in 15 or 20 years from this time, the stars may 

 be expected to appear in contact, or to^ be actually occulted one 

 by the other, as has recently been observed to happen to 7 Vir- 

 gin is. 4. A list of the Approximate Places of 15 Planetary and 

 Annular Nehulce of the Southern Hemisphere, discovered loith 

 the 2Qfeet Reflector ; with Uraivings illustrative of the Appear- 

 ance and structure of 3 principal Nebulm in the Southern Hem- 

 isphere. These are arranged in order of R. A. and numbered. 

 Among these, several are somewhat elongated, and offer the ap- 

 pearance of being double. No. 7 is of a fine blue color, and 

 being particularly well-defined, has exactly the aspect of a blue 

 planet. No. 4 is a very bright and considerably large elliptic 

 disc of uniform light, on which, but excentric, is placed a pretty 

 large star. Several are very small ; No. 15 is not more than Z" 



