VOL. LXXtl 



•] 



PHILOSOPHICAL TRANSACTIONS. 



223 



24. In constellatione Ceti, Fl. 37. 



Oct. 12. Double. It is a star between i and 

 towards the north. Distance 42".8 12, inaccurate. 



25. r Ononis, Fl. 20, supra talum in tibia. 



Oct. 23. — Double. Very unequal. Distance 

 about 30". 



26. h Leonis, Fl. 6. 



Feb. 21, 1781. — Double. Very unequal. Lr; 

 S d. Distance 36" 9'". Position 12° 55' n following. 



27. In constellatione Libras, near Fl. 31. 



May 24-. Double. The most south of 3 small 

 stars in the finder. Equal, or the preceding rather 

 the larger. Both w inclining to pale r. Distance 

 44" 12'", a little inaccurate. Position 40° 17' s 

 following. 



28. In constellatione Cephei. 



May 27. — ■ Double. It is a star near S. Ex- 

 tremely unequal. Distance about 30". 



29. ' Serpentis, Fl. 53. Post dextrum femur Ser- 

 pentarii. 



July 10". — Double. Unequal Distance about 35". 



30. In constellatione Serpentarii, Fl. 53. 



July l.Q. — Double. It is a star between «■ and $ ^ 

 of the way from «. Very unequal. L w ; S in- 

 clining to r. Distance 32" 21'", narrow measure. 



3 1 . In constellatione Aquilae. 



j u ]y 19, — Double. It is the star next but one pre- 

 ceding ^. Very unequal. L r ; S d. Distance 

 about 30". 



32. « Andromedae. 



July 21— Double. Extremely unequal The 

 small star better with 460 than with 227- L w ; S 

 d. Distance 55" 32'", rather narrow measure. 

 Position 10° 37' s preceding. 



33. h Aquilae, Fl 15. 



July 25. — Double. Unequal. Both pale r Dis- 

 tance 33" 53", inaccurate. 



34. In constellatione Aquilae, A Fl. 28. 



July 25. — Double. It is one of 2 stars near A. 

 Distance about 35". 



35. In constellatione Aquilae- 



July 25. — Double. It is a star near that which 

 follows C. Very unequal Distance about 40". 



36'. o Scuti, Fl. 2, in constellatione Aquilae. 



July 30. — Double Very unequal. L pale r ; S d. 

 Distance 42" 44'", a little inaccurate. 



37. <> Coronae, Fl. IS. 



Sept. 21. — Treble. Very unequal. L w ; S both r. 

 Dist. of the nearest about 50" ; the farthest I h min.* 



38. In Constellatione Herculis, Fl. 23. 



Sept. 21. — Double. It is the star between » and % 

 Coronae, the largest of a telescopic triangle. Dis- 

 tance 36" 27'", rather narrow measure. L w ; S w ; 

 inclining to r. 



39. x Lyrae, Fl. 3. In testa fulgida. 



Sept. 24. — Double. Excessively unequal. By 

 moonlight I could not see the small star with 278, and 

 saw it with great difficulty with 460 ; but in the 

 absence of the moon I have seen it very well with 227. 

 L fine brilliant w; S dusky. Distance 37" 13'". 

 Position 26° 46' s following. 



* In a future collection the small star at the obtuse angular 

 point will be found as a double star of the id or 3d class. 



Oct. 22. Having often measured the diameters of 

 many of the principal fixed stars, and having always 

 found that they measured less and less the more I mag- 

 nified, I fixed on this fine star for taking a measure 

 with the highest power I have yet been able to apply, 

 and on the largest scale of my new micrometer I could 

 conveniently use. With a power of 6*450 (determined 

 by experiments on a known object at a known distance) 

 I looked at this star for at least a quarter of an hour, 

 that the eye might adapt itself to the object; having 

 experimentally found, that the aberration by this 

 means will appear less and less, and, in the telescope 

 I used on this occasion with powers from 400 to 1500, 

 will often quite vanish, and leave a very well-defined 

 circular disc for the apparent diameter of the stars. 

 The diameter of « Lyrae, by this attention, appeared 

 perfectly round, and occasionally separated from rays 

 that were flashing about it. From the very brilliant ap- 

 pearance of the star with this great power, and a pretty 

 accurate rough calculation founded on its apparent 

 brightness, when observed with the naked eye with 

 227, with 460, with 6+.">0, I surmise, that it has 

 light enough to bear being magnified at least a hun- 

 dred thousand times with no more than 6 inches of 

 aperture, provided we could have such a power, and 

 other considerations would allow us to apply it. When 

 I had as good a view as I expected to have, I took its 

 diameter with my new micrometer on a scale of 8 

 inches and 4428 ten thousandth to 1" of a degree, and 

 found it subtended an angle of t)".3553. I had no 

 person at the clock ; but suppose the time of its pass- 

 ing through the field of my telescope, which in this 

 'great power is purposely left undefined, and as large 

 as possible, was less than 3 seconds. 



40. » Lyrae, Fl. 8. 



Sept. 24. — Treble. Extremely unequal. L w ; 

 S both d. One n preceding, the other s following. 

 Distance of the following star 56" 47'", a little inac- 

 curate. Position of the same 28° 27' s following. 



41. APersei, Fl. 43. 



Sept. 24. — Double. Unequal. L w. Distance 

 about 50". 



42. In constellatione Lyrae. 



Sept. 25. — Double. It is a small star just by 0. A 

 little unequal. Both r. Distance 38" 8"'. Position 

 26° 18' n following. 



43. In constellatione Cygni, Fl. 76'. 



Oct. 1. — Double. It is the 3d star from f towards 

 v. Unequal. Distance 48" by exact estimation. 

 Position — preceding. 



44. In constellatione Cygni, Fl. 69. 



Oct. 1. — Treble. Very unequal. L w; S both 

 reddish. Position — preceding. 



45. In constellatione Cygni. 



Oct. 1.- Double. It is the more south of 2 teles- 

 copic stars following -r. Very unequal. L w ; S d. 

 Distance 44" by exact estimation. Position — following. 



46. c Cygni, Fl. 16. l" ad c. 



Oct. 5. — Double. It is the star next following 8. 

 Almost equal. Both pale r. Distance 30", by pretty 

 exact estimation. 



47. c Cygni, Fl. 26. 2 a ad c. 



Oct 8. — Double. Very unequal. L reddish w ; 



