580 BIBLIOGRAPHY OF HERSCHEL's WRITINGS. 



Hersch.el, W.: Svxorsis of the Writings of— Continued. 



A. D. Vol. P. 



1802 92 221 Of the Appearances of the new stars with regard to a Disk. 



Ceres has a visible disk. Pallas^ disk I would ratlier call a nucleus. 

 221 Of the appearances of the new stars, with regard to an atmosphere or coma. 



[Observations] probably no coma. 

 223 On the nature of the new Stars. 



223 What are these new stars; are they planets or are they comets? 



224 Planets defined (by 7 particular properties). 



225 Our new stars cannot be called planets. 



226 Comets defined (by 5 particular properties). 



228 The new stars are not comets. They should be called Asteroids from 



their resemblance to small stars. 



229 Asteroids defined. 



229 Statement of the reasons we have for expecting that additional aste- 

 roids may probably be soon found out. 



229 I have already made five reviews of the zodiac without detecting^any 



of these asteroids; their motion and not their appearance will bo 

 the future means of detecting them. 



230 We have reason to believe that a number of asteroids may remain con- 



cealed. 



230 Comets may become asteroids. 



231 Additional observations relating to the appearances of the asteroids Ceres 



and I'allas. 

 The coma of Ceres not much greater than that of stars of the same 

 magnitude. 



232 The fixed stars differ considerably in this resiJect among themselves. 

 232 The coma of Pallas not much more than for equal fixed stars. 



1802 92 477 Catalogue of .500 nciv Xebulce, nebulous Stars, planetary ncbulcB and Clus- 

 lei's of Stars; with Remarks on the construction of the Heavens. By 

 William Hersciiel, LL. D., F. R. S. Read July 1, 1802. 

 After a sufficient number of celestial objects is found, there is a neces- 

 sity for a scientific classification. The former classification was 

 only for the convenience of the observer. 



478 Enumeration of the parts that enter into the construction 



OF the heavens. 

 I. Of Insulated Stars. 



479 Notion of an insulated star — our sun is one. 



480 The milky way consists of stars very difi"erently scattered from those 



which are immediately about us. 

 480 By analogy we may admit that every insulated star may be attended 

 with planets, etc. I should hesitate to extend this analogy to every 

 star in the heavens, and even think that probably we can only look 

 for solar systems among insulated stars. 



480 II. Of Binary Sidereal Systems or Double Stai-s. 



481 Difference between a double and a binary star. 



482 Difference between solar and sidereal systems. 



482 No insulated stars of nearly an equal size and distance can appear 



double to us. 



483 Proof of this. 



485 Casual situations will not account for the multiplied phenomena of 



double stars, and their existence is owing to a general law of na- 

 ture — gravitation is that law. 



486 I shall soon communicate a series of observations on double stara, 



proving that many of them have already changed their situation with 



