NEBULiE, CLUSTERS, ETC. 23 



Herschel, W. : Abstracts of Memoirs — Continued. 



A. D. Vol. P. 



1791 81 71 On Nebuloits Stars properly so called. 



The name nebulous stars incorrectly used in former times. 



72 Nebulae 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 interme- 

 diate 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 led to the belief that all 



nebulae were clusters more or less remote. 

 Basis for the ideas of connection and disjunction of stars 

 and nebulae. 

 75-77 Particular examples of such supposed conjunctions and 

 disassociations. 

 The trapezium of Orion is unconnected with the nebula. 

 78-82 Notes of observations on nebulous stars and consideration 

 of the relation of the nucleus to the envelope in each 

 case. 



83 Considering H, iv 69, [= G. C. 810,] as a typical nebu- 



lous 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 

 admit that the star is involved in a shining fluid of a 

 nature totally unknown to us. 



84 The telescopic milky way is probably composed of this shin- 



ing fluid, which must commence somewhere about the 

 range of the stars of the 7th magnitude, and extend to 

 the regions of the 9th, 10th, 11th, and 12th. 

 83 The shining fluid might exist independently of stars. The 

 light of this fluid is no kind of reflection from the star 

 in the centre. If this matter is self-luminous, it seems 

 more fit to produce a star by its condensation than to 

 depend on the star for its existence. 



86 List of diffused nebulosities and planetary nebulae; both 



better accounted for by the hypothesis of a shining fluid 

 than by supposing them to be distant stars. 

 Regeneration of stars from planetary nebulae. 



87 How far the light-corpuscles emitted from millions of suns 



may be concerned in this shining fluid it is not neces- 



