BIBLIOGRAPHY OF HERSCHEL^S WRITINGS. 547 



Herschel, W.: Synopsis of the Wiiitixgs of— Continued. 

 A. D. Vol. P. 



1790 80 479 As obsiTvations, carefully made, should always take tlie lead of theo- 



ries, I shall not he concerned if what I have to say contradicts what 

 has been said in my last paper. 

 479 A lucid and apparently protuberant point may exist without any 

 great inequality in the ring. A vivid light, for instance, will seem 

 to project greatly beyond the limits of the body upon which it is 

 placed. 



479 The brightest and best-observed spot agrees to a revolution of 10^ 32™ 



15^4 at a distance of 17". 227, i. e., on the ring. Therefore, unless 

 the ring is fluid, or has a gi-oove in it, so as to let the satellite re- 

 volve in it, we ought to admit a revolution of the ring itself. 



480 It seems almost proved that the consistence of the ring is not less than 



the body of Satiirn ; consequently no sufficient degree of fluidity 

 can be admitted. 



481 Observations not accounted for iy satellites [are given], 

 487 Epochs of six of the satellites given. 



487 Period of Enceladus l^ 8^ 53™ 8^9 ; distance 36".7889. 



" ''Mimas 0^ 22i^ 37™ 22^9 ; " 28".6689. 



488 Tables for the seven satellites of Saturn. 

 495 Example of the use of the tables. 



1791 81 71 On Nebulous Stars, 2)roperly so called. By William Herschel, LL.D., 



F. R. S. Read February 10, 1791. 

 71 In one of my late examinations of the heavens I discovered a star of 



about the 8th magnitude, surrounded with a faintly luminous atmosphtra 



of a considerable extent. 

 71 The name nebulous stars was incorrectly used in former tim^s. 



71 The milky way itself consists entirely of stars. 



72 Nebulas can be selected so that an insensible gradation shall take place 



from a coarse cluster like the Pleiades down to a milky nebulosity 

 like that in Orion, every intermediate step being represented. This 

 tends to confirm the hypothesis that all are composed of stars more 

 or less remote. 



73 A comparison of the two extremes of the series, as a coarse cluster and 



a nebulous star, indicates, however, that the nebulosity about the star 

 is not of a starry nature. 



74 Summary of the reason which formerly led to the belief that all 



nebulae were clusters more or less remote. 

 Basis for the ideas of connection and disjunction of stars and nebulne. 

 75-77 Particular examj)les of such supposed conjunctions and disassocia- 

 tions. Telescopic milky way of over 60 square degrees. 

 The trapezium of Orion is unconnected with the nebula. 

 78-82 Notes of observations on nebulous stars and consideration of the re- 

 lation of the nucleus to the envelope in each case. 



83 Considering H, iv 09, [= G. C. 810,] as a typical nebulous star, and 



supposing the nucleus and chevelure to be connected, we may, 1st, 

 suppose the whole to be of stars, in which case either the nucleus is 

 enormously larger than other stars of its stellar magnitude or the 

 envelope is composed of stars indefinitely small; or, 2d, we must ad- 

 mit that the star is involved in a shining fluid of a nature totally 

 unknown to us. 



84 Perhaps it has been too hastily surmised that all milky nebulosity ia 



owing to starlight only. 



