BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 539 



Herschel, "W.: Synopsis op the Wiutixgs of— Continued. 

 A. D. Vol. P. 



1785 75 241 The stars being supposed to be nearly equally scattered, and th.-ir 



number in a field of view of known angular diameter being given, 

 to determine the length of the visual ray. Solution of the problem. 



243 Another solution. 



244 We inhabit the planet of a star belonging to a Compound Nebula of the 



third form. 

 244 Proof that the sun is situated in a compound nebula of Form III. 

 250 Use of the gauges. 



253 Section of our sidereal system. ' 



254 The origin of nebulous strata. • 



256 An Opening in the Heavens. M. 80 and M. 4 on the edges of vacancies. 



257 Phenomena at the Poles of our nebula. 



258 Enumeration of very compound ncbnlw or milky ways. Ten described, in- 



cluding those of Orion and Atidromcda. 

 263 A Perforated Nebula or liing of Stars. Account of nebula of Zyra. G. C, 



4447. 

 Planetary nebula;. Observations of G. C, 4G28, 4964, 4572, 4565, 826, 



2102, 4302. 

 266 The accompanying plate, viii, gives a figure of a section of the milky 



way. 



1786 76 457 Catalogue of one thousand Neio Nebula and Clusters of Stars. By Wil- 



liam Herschel, LL. D,, F. R. S. Read April 27, 1786. 



457 Description of sweeping telescope ; Newtonian; 20 feet focus, 18.7 in. 



aperture, power 157, field 15' 14". 



458 Description of the method of sweeping. 



464 Probable errors of the places given by the sweeps before 1783, Dec. 

 13, Aa=l>°; ^5 8'-10', during 1784 j\a<30^; A(5 <5'. 

 Till 1785, September 24, Aa<12s; ^S <4'. 

 Till 1786, April, Aa < 6^ ; A(5 < 2'. 



466 When the diurnal motion of the earth was first maintained it could 

 not but add greatly to the reception of this opinion when the 

 telescoj)e showed Jupiter, Mars, and Venus revolving on their axes ; 

 in the same way the view of so many sidereal systems will add 

 credit to what I have said in regard to the construction of the 

 heavens. For to the inhabitants of the nebulae of the present cata- 

 logue our sidereal system must appear either as a small nebuloas 

 patch ; an extended streak of milky light ; a large resolvable neb- 

 ula ; a very compressed cluster of minute stars, hardly discernible ; 

 or as an immense collection of large scattered stars of various sizes, 

 according as their situation is more or less remote from ours. 



466 Definition of classes of nebulaj and clusters. 



467 A map of positions of nebulae Avas made for identification [by means 



of which the laws of aggregation of the nebulae were gradually dis- 

 covered]. 

 469 Explanation of a short method of describing the appearance of a neb- 

 ula by letters, 



