318 a A. Young on the Solar Cm^ona. 



to refer to Mr. Proctor's recent work on tlie sun, and to a paper 

 which Professor Norton has published in a late number of this 

 Journal, wherein his views are fully explained. According to 

 this view, the leucosphere and the rays are alike solar appen- 

 dages, and of identical origin and material. 



The theory of Oudemans is stated in a letter to " Nature," 

 contained in the number for Nov. 10, 1870. 



With good weather, it would seem possible to decide be- 

 tween these two hypotheses at the next eclipse, 



A series of corona photographs taken as rapidly as possibk 

 on the plan pursued by Mr. Brothers (who has shown tliat an 

 exposure of from 8 to 10 seconds is sufl&cient to produce a fine 

 picture) would probably indicate whether the dark streaks are 

 really related to mountains on the edge of the moon or not. 



It 'is probable also, as Prof. Pickering has suggested, that im- 

 portant information may be obtained by observing them with a 

 spectroscope of high dispersive power and widely opened slit. 

 using the 1474 line just as the C line is used in examining the 



The telescope, to which the spectroscope employed for the 

 purpose is attached, should be of wide angular aperture, so as 

 to give abundant hght, but of very short focus, forming an 

 image of the sun not much more than | of an inch in diameter, 

 in order that the rays may be so little magnified that their out- 

 line, if they are really of leucospheric origui and give the green 

 monochromatic light, may be readily observed through the sJit 



There remains still unsettled another interesting series of 

 questions concerning the nature of the substance composing tlie 

 leucosphere, and the relation of this envelope to the sun: 

 whether it be a true atmosphere, or a mere cloud of transient 

 particles — a meteor-flock, as Mr. Proctor imagines. 



Apart from the diflficulty of supposing such a multitudinous 

 and continual supply of meteoric matter as this theory wouia 

 require, and neglecting all consideration of the peculiar toiin 

 assumed by this envelope, which seems to be deepest precisei^^ 

 over those solar latitudes where the spots and prominences aie 

 most numerous, and even to be governed in the minutiae ot i^ 

 outline by the position of its prominences, I find w^hat seems . 

 me an almost insuperable objection to it in the powerful wim = 

 and cyclones which prevail in the region above the cliromo 

 sphere at elevations of from 50,000 to 100,000 miles. 



These winds, by which the tops of the solar Aames ai 

 ^vl^irled and driven, present, so far as obsei-^-ations n<^^^." 

 every characteristic of true aerial currents in a continuous lu 

 dium ; and the whole appearance and behavior of the solar F 

 tuberances, except at the moment of eruption, is that ol clou 

 floating in an air. 



