oj DvuhU Stars. 45 



• AW the obierviitions in the following catalogue on the rela- 

 tive magnitude, colour, and pofition of the flars, are to be 

 underftood as having been made with a power of 460, unlefs 

 thcv are marked otherwife. This will account fo.r t!ie dif- 

 fereiice which obfervers may find in. the relative magnitude ; for 

 fhould they ufe only a power of about 200, many of the 

 fmali ftars that are lliid to be very unequal and extremely une- 

 qual, muft appear to them perhaps a degree lower in the fcale, 

 and become extremely and exccliively unequal : and this will 

 happen, though the quantity of light fhould be the very fame 

 which the refledtor has that ferved me to fettle thefe particulars. 

 I need not fay, that on other accounts, fuch as a real difference 

 in the light of the telefcope, the pre fence of the moon, twi- 

 lights, aurorse boreales, or other eaufes, many of the fmall 

 flars may be found to be of a different comparative luflre from 

 what is afligned to them In the catalogue. The fmall ftar near 

 Rigel, for Inftance, appears of a beautiful pale red colour, full,, 

 round, and well defined, with my 20-feet reflector j the lo-feet 

 inflrument fhews it alfo very well in fine evenings ;. the ^-feet 

 requires more attention, nor is the Imall flar defined, but of a 

 duiky pale red colour. A good 3I feet achromatic, of a large 

 aperture, when Rigel is on the meridian,, may, perhaps, alfo 

 f-iew the fmall flar, although 1 have not been able to fee it 

 with a very good inftrument of that fort, which fhews the 

 fmall flar that accompanies the pole-flar ; but the evening was 

 not very favourable. 



The meafures of the diflances were all taken with a parallel 

 filk- worm's- thread micrometer, and a power of 227 only.. 

 They are not, as in the former catalogue, with the diameters 

 included^ hut fi"om the center of one f}:ar to the center of the 



other.. 



