22t) PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



Oct. 22. — Multiple It is one star with at least 12 star, when on the meridian, measured 1' 4(>' ', a 



around it, all within the field of my telescope mean of 2 very complete observations, they agreed to 



66 aTauri, Fl. 87. Splendida in austrina oculo. 6'"; with 932, it measured 1" Vi" , also a mean of 2 



j)ec. 1<). — Double. Extremely unequal. L r; excellent observal ions ; they agreed to S'". The ap- 



S d. Distance I' 27" 45'", position 52° 58' n fol- parent disc was perfectly well defined with both 



lowincr. With -tn'O, the apparent diameter of this powers. 



Postscript to the Catalogue of Double Stars. — Since having delivered my paper 

 on the parallax of the fixed stars, in which I refer to the above catalogue of 

 double stars, I have received the 4th volume of the Acta Acadeiniae Theodoro 

 Palatinae, which contains a most excellent Memoir of Mr. Mayer's, " De novis 

 in Ccelo sidereo Phaenomenis ;" where I see that the idea of ascertaining the 

 proper motion of the stars by means of small stars that are situated at no great 

 distance from large ones, has induced that gentleman before me to look out for 

 such small stars. In the course of that undertaking he has discovered a good 

 many double stars, of which he has given us a pretty large list, some of them 

 the same with those in my catalogue. My view being the annual parallax, re- 

 quired stars much nearer than those that would do for Mr. Mayer's purpose; 

 therefore I examined the heavens with much higher powers, and looked out 

 chiefly for such as were exceedingly close. 



The above catalogue contains 269 double stars, 227 of which, to my present 

 knowledge, have not been noticed by any person. I hope they will prove no in- 

 considerable addition to the general stock, especially as in that number there are 

 a great many which are out of the reach of Mr. Mayer's and other mural qua- 

 drant or transit instruments. It can hardly be expected, that a power of 70 or 

 80 would be sufficient to discover those curious stars that are contained in the 

 first class of my catalogue ; so that it is not strange they should have entirely 

 escaped Mr. Mayer's notice. We see that it is not for want of his looking at 

 those stars ; for we find he has frequently observed £ Cancri, the star near 

 Procyon, and the star in Monoceros, without perceiving the small stars near 

 them, which I have pointed out. Nor is it only in the first class that his tele- 

 scope wanted power, light, and distinctness ; for the small stars that are near 

 j3 Ononis, (3 Serpentis, ^Ononis, e Pegasi, a. Lyrae, aAndromedae, ju. Sagittarii, 

 a Aquilae, n Pegasi, $ Lyrae, i Librae, x Piscium, ?. Tauri, and many more, 

 have escaped his discovery, though he has given us the places of other more 

 distant small stars not far from them, and therefore must have had them fre- 

 quently in the field of view of his telescope. In settling the relative situations 

 of very close double stars, neither Mr. Mayer's instruments, nor his method, 

 were adequate to the purpose. It is well known, that whenever we employ time 

 as a measure, the results cannot be very accurate ; because a mistake of no more 

 than a 10th part of a second in time will produce an error of a whole second 

 and a half in measure, so that his ar must be extremely defective. Nor could 



