Hoxjul Aslrotiomical Society. 137 



It is almost unnecessary to say that the reductions have been 

 made on the best existing data, and according to the most approved 

 methods. 



On Luminous Rings round Shadows. By the Rev. Baden Powell, 

 Saviliun Professor of Geometry, Oxford. 



Tlie remarkable optical phcenomena attending total solar eclipses, 

 especially the formation of a luminous ring round the discs, are now 

 on the whole so well established, that speculations have been ha- 

 zarded as to their cause : and though these speculations as yet 

 scarcely amount to more than very general illustrations, yet as ex- 

 perimental facts have been elicited which seem to bear a resemblance 

 to the phenomena in question, they deserve notice, even in the pre- 

 sent uncertain state of the inquiry. 



The author disclaims any idea of bringing forward such facts as 

 a complete explanation ; but he is induced to offer them because one 

 experiment devised by him long since was thought by the late Mr. 

 Baily worthy of being laid before the Society, though communicated 

 to him without any such intention. (Ast. Soc. Notices, March 10, 

 1843.) 



The following is the author's historical summary of the observa- 

 tions of the luminous ring : — 



The pheenomenon appears to have been observed as early as the 

 time of Plutarch, as appears by a passage from him cited in the 

 Comptes Reiulus, 1842, i. 847. In more modern times, probably the 

 earliest recorded instance is in the eclipse of 1567 [this is clearly 

 wrong in date or name] observed by Kepler. The ring was observed 

 at Naples in 1605 (Phil. Trans, vol. xl. 177) ; and from the year 

 1 706 we have the full and well-known records of the most eminent 

 astronomers down to the present day, which establish the phaeno- 

 menon as a regular part of the appearance of a total eclipse. The 

 author refers to instances in the Mem. Ast. Soc, vol. i. p. 144, and 

 vol. x. p. 9-16, 37, &c., and to the Notices of this Society, vol. v. 

 p. 207 ; as also to the Comptes Rendvs for 1842, parts 1 and 2. He 

 remarks that remarkable discrepancies are found in the accounts of 

 the same, as well as of different eclipses, and he mentions instances. 

 Some of these discrepancies admit of easy explanation. In the tran- 

 sit of Venus in 1769 light was seen surrounding the part of the pla- 

 net off the sun, both at immersion and emersion ; but this has been 

 ascribed to her atmosphere. (Ast. Soc. Mem. vol. x. p. 27.) The 

 aiwgnhxr profiiherances observed in the eclipses of 1733 and 1842 do 

 not seem to belong to the ring ; and it seems to the author hardly con- 

 ceivable that they can be purely optical phenomena, as suggested 

 by M. Valz and M. Arago. 



Tlie author next gives an account of the attempts of different 

 astronomers to assign « cause for the luminous ring. Kepler con- 

 sidered it to be due either to combustion round the sun, or to refrac- 

 tion of his rays b)- the moon's atmosjihere. Others have more ge- 

 nerally attributed it to some j;eculiar effect of the solar atmosphere ; 

 and some, especially Olbers, expressly attribute it to the zodiacal 

 light. De risle, and more lately Arago and Valz, regard it altogether 

 P/iil. Mag. S. 3. Vol. 30. No. 199. Ffb. ISi?. L 



