BISHOP'S RING AROUND THE SUN. 471 



as Bishop's ring. It is for the meteorologist to inquire whether a sup- 

 ply of dust sufficient in quantity and quality, appearing at the right 

 time and enduring long enough, can be accounted for. 



Kiessling, of Hamburg, already referred to, has done the best work 

 on the corona as well as on the great sunsets with which it is evidently 

 connected. His pamphlet, entitled "Die Dammerungserscheinungen 

 im Jahre 1883, und ihre physikalische Erklarung " (Hamburg, 1885), 

 gives the most satisfactory account and explanation of the twilights 

 that I have seen ; and its value is largely increased by the experi- 

 mental illustrations that the author has devised in imitation of the 

 strange natural phenomena that he accounts for so well. A later 

 paper, " Ueber die geographische Verbreitung des Bishop'schen Son- 

 nenringes," in the May number of the little meteorological journal, 

 " Das Wetter," and a short paper by Forel on " Le Cercle de Bishop," 

 in the Geneva " Archives des Sciences " for June, are the most recent 

 articles of consequence on the corona, and give important evidence as 

 to the origin of its diffraction particles by showing its relation to the 

 famous sunsets. The new corona was first noticed in Honolulu on the 

 5th of September, 1883, by the Rev. Sereno F. Bishop, who called 

 attention to it by descriptions published at the time, and in letters to 

 "Nature." Although seen so early in September in the Sandwich 

 Islands, it was not recognized in this country till November 24th, when 

 Professor Le Conte saw it at Berkeley, California ; nor in Europe till 

 the days directly following ; but ever since then it has been continu- 

 ously visible till now, in proper conditions of weather as already de- 

 scribed. After rarely being seen in the summer, it has reappeared in 

 the clearer days of the winter. Being always relatively inconspicu- 

 ous, the date of its first visibility can not generally be determined 

 with accuracy — alas for the neglect of so rare an opportunity of val- 

 uable observation ! — but the agreement of the growth of the area in 

 which it was noted and the spread of the great sunsets is placed be- 

 yond a doubt ; and with them its origin must be referred to the explo- 

 sive eruption of Krakatoa. Kiessling considers this relation of cause 

 and effects to be firmly established, and even quotes approvingly 

 the name given by Arcimis in Madrid, "corona solar krakatoense," 

 although the name of "Bishop's ring" is undoubtedly the one that 

 will come into general use. 



The evident difficulties in the way of accepting the volcanic origin 

 of the diffracting particles are the great quantity of material that 

 would seem to be needed, the excessive fineness of its texture, and 

 its long suspension in the thin upper air ; but I believe that these diffi- 

 culties are by no means fatal to the volcanic theory. The quantity 

 needed is not absolutely so great, after all. Tyndall suggested that 

 the minute, almost molecular particles, to which the blue color of the 

 sky is usually referred, could all be contained in a snuff-box ; and, 

 while this need not be taken as in any way an accurate estimate of the 



