BIBLIOGRAPHY OF IIERSCHEL^S WRITINGS. 001 



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



A. D. Vol. p. 



that the effect of the solar agency depends entirely upon the state 

 of the uebulons matter of Avhich the conust is composed. This 

 second comet had probably but little unjurihclioncd matter. 



1812 102 236 If, then, the effect of the sun on comets is more or less conspicuous, 

 according to the amount of unperihelioned nebulous matter which 

 they contain, we may arrange these celestial bodies in a certain 

 order of consolidation, from which, in the end, a considerable in- 

 sight into their nature and destination may be obtained. 



236 For example, the comet of this paper is of such a construction that 



it was but little more affected by its perihelion passage than a 

 planet would have been. It was in a very advanced state of con- 

 solidation. 



237 That of 1807 was more affected, and, although considerably condensed, 



conveyed a great quantity of nebulous matter to the perihelion 

 passage. That of 1811 contained, with little solidity, a most 

 abundant portion of nebulous matter. 



1814 104 248 A.'itronomical Olservaiions relating to the Sidereal part of the Heavens and 

 its Connection tcith the Nebulous part; arranged for the purpose of a 

 critical examination. By William Herschel, LL. D. , F. R. S. Read 

 February 24, 1814. 

 In the memoir on the nebulous part of the heavens iPhil. Trans-^ 

 1811] I have endeavored to show the probability of a very gradual 

 conversion of the nebulous matter into the sidereal appearance. 

 This paper refers to the sidereal part of the heavens. 



249 I- Of stars in remarkable situations in regard to Xcbulw. 



Surmise that nebuhe may have considerable proper motions. Neces- 

 sity of caution in such conclusions. Five stars in such situations. 



250 II. Of two stars with nebulosity between them. 



19 instances of such connection are given ; in the memoir of 1811, 13G 

 double nebula} joined by nebulosity were noted. 



251 Should we not surmise that possibly these stars had formerly been 



bi-hlv condensed nebuhu Uke those that had been mentioned, and 

 wire now by gradually increasing condensation turned into small 

 stars- and may not the nebulosity still remaining show their neb- 

 ulous ori-rin ? Also as we have over 700 double stars free from neb 

 ulosity, many of which are probably at no great real distance from 

 us It seems as if we might have these double objects in three differ- 

 ent successive conditions. First, as nebuhe ; next as stars with re- 

 maining nebulosity; and lastly, as stars completely free from neb- 

 ulous appearance. ,,,,,., 



251 III. Of stars ivith nebulosity of various shapes attached to them. 



2.^2 Fourteen such objects noted. 



Now if we admit a contact between these nebuhe and the stars, it 

 deserves to be remarked that stars in the situation of these four- 

 teen cannot have been formed from their adjoining nebulosities; 

 for a gradual condensation of the nebulous matter would have been 

 central; whereas the stars are at the extremity of he nebuhe 

 Their cmmection is then due to some motion either of the star or of 

 the nebuhe. If the nebulosity should subside into the star, it 

 would give an idea of the groivth of a star. 



9^'\ TV Of stars ivith nebulotis branches. , , , i p 



iLfca °8 uolcJ of a c«n„»c,Lou between staw ami nebuhe, anj ef- 



j:ZZa. to FkU. Tran.., 1611, „.. 301-3U, for further examples. 



