210 Mr. William Euggins [Feb. 20, 



Mr. Proctor, on the gronnd tliat there must be such streams crowding 

 richly together in the sun's neighbourhood. 



6. The view of the corona suggested by Sir William Siemens in 

 his solar theory. 



It has been suggested, even, that the corona is so complex a 

 phenomenon that there may be an element of truth in every one of 

 these hypotheses. Any way this enumeration of hypotheses more or 

 less mutually destructive, shows how great is the difficulty of ex- 

 plaining the appearances which present themselves at a total solar 

 eclipse, and how little we really know about the corona. 



An American philosopher, Professor Hastings, has revived a prior 

 and altogether revolutionary question : Has the corona an objective 

 existence ? Is it anything more than an optical appearance depending 

 upon diffraction ? Professor Hastings has based his revival of this 

 long discarded negative theory upon the behaviour of a coronal line 

 which he saw, in his spectroscope, change in length east and west of 

 the sun during the progress of the eclipse at Caroline Island. His 

 view appears to rest on the negative foundation that Fresnel's theory 

 of diffraction may not apply in the case of a total eclipse, and that 

 at such great distances there is a possibility that the interior of the 

 shadow might not be entirely dark, and so to an observer might cause 

 the appearance of a bright fringe around the moon.* 



Not to speak of the recent evidence of the reality of the corona 

 from the photographs which have been taken when there is no inter- 

 veninfi- moon to produce diffraction, there is the adverse evidence 

 afforded by the peculiar spectra of different parts of the corona and by 

 the complicated and distinctly peculiar structure seen in the photo- 

 graphs taken at eclipses. The crucial test of this theory appears 

 to be, that if it be true, then the corona would be much wider 

 on the side where the sun's limb is least deeply covered, that is to 

 say the corona would alter in width on the two sides during the 

 progress of the eclipse. Not to refer to former eclipses where photo- 

 graphs taken at different times and even at different places have been 

 found to agree, the photographs taken during the eclipse at Caroline 

 Island show no such changes. M. Janssen ssijs : " Les formes de 

 la couronno ont ete absolument fixes pendant toute la duree do la 

 totalite." The photographs taken by Messrs. Lawrence and Woods 

 also go to show that the corona suffered no such alterations in width 

 or form as would be required by Professor Hastings' theory during 

 the passage of the moon. 



We have therefore, I venture to think, a right to believe in an 

 objective reality of some sort about the sun corresponding to the 

 appearance which the corona presents to as. At the same time some 

 very small part of what we see must be due to a scattering of the 



* Koport of tlic Eclipse Expedition to Caroline Islaml, May 1883. Memoir 

 of the National Academy of Sciences, Wasbington. 



