550 BIBLIOGRAPHY OF HERSCHEL^S WRITINGS. 



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

 A. D. Vol. P. 



1792 82 23 Miscellaneous observations. By AVilliam Hekschel, LL. D., F. R. S. 



Read. December 22, 1791. 



23 Account of a Comet. [1792, I.] This was discovered by Carolina 



Herschel, 1791, Dec. 15. Examined Dec. 16 with a 20-foot re- 

 ilector; brief description and position for Dec. 10. 



24 On the periodical appearance of o Ceti. 



25 331 days IQi^ W^ is its period. 



26 On the disappearance of the hhth Herculis. 



1781, Oct. 10, I examined both 54 and 55 Herculis; again 1782, April 

 11 ; 1790, May 24, 55 Herculis was missing, and although looked for 

 has not again been seen. 



27 Remarlcahle Phenomena in an eclipse of the Moon. 



1790, Oct. 22, when the moon was totally eclipsed I viewed the disc 

 with a 20-feet reflector with power 360. In several parts of it I 

 perceived many bright, red, luminous points. Most of them W' re 

 small and round, at least 150 of them. Their light did not much 

 exceed that of Movs Porphyrites Hevelii. 



We know too little of the surface of the moon to venture at a surmise 

 of the cause from whence the great brightness, similarity, and re- 

 « markable color of these points could arise. (Dated) Slough, De- 



cember 17, 1791. 



1793 83 201 Observations on the Planet Venns. By William Herschel, LL. D., 



F. R. S. Read June 13, 1793. 



201 A series of observations on Venus begun in April, 1777, has been con- 



tinued down to the present time. The lirst object of the research 

 was to determine the diurnal rotation, for the observations of Cas- 

 SINI and Bianchini can leave no doubt but that it has a rotation 

 on its axis; the second was the atmosphere of Venus, of tin', exist- 

 ence of which, after a few months' observations, I coukl not enter- 

 tain the least doubt ; and third, the investigation of the real diam- 

 eter. To which may be added an attention to the construction of 

 the planet with regard to permanent appearances, such as might be 

 asciibed to seas, continents, or mountains. 



202 The result of my observations would have been communicated long 



ago if I had not flattered myself with the hope of some better suc- 

 cess concerning the diurnal motion of Venns, which has still eluded 

 my constant attention as far as concerns its period and direction. 

 202 Even at this present time I should hesitate to give the following ex- 

 tracts if it did not seem incumbent upon me to examine by what 

 accident I came to overlook mountains in this planet '^ of such enor- 

 mous height as to exceed four, Jive, or even six times the perpendicular 

 elevation of Chimborago, the highest of our mountains." [Quoted from 

 Schroeter, Phil. Trans. 1792, p. 337.] 



202 The same paper contains other particulars concerning Venus and 



Saturn. AU of which being things of which I have never taken 

 any notice, it will not be amiss to show by what follows that neither 

 want of attention nor a deficiency of instruments could occasion my 

 not perceiving tliese mountains of moi-e than 23 miles in height; this 

 jagged border of Venus; and these flat spherical forms on Saturn. 



203 Before I remark on the rest of the extraordinary relations above men- 



tioned I will give a short extract of my observations of Venus. 

 203 Observations from 1777, April 17, to 1793, May 20. 



