1885. J on the Solar Corona. 209 



matter iu the wroug place so far as astrouomical observations are 

 concerned, and iu a peculiar degree for success in j^liotographing 

 the corona. We are only beginning to learn tbat wbetber in our 

 persons or in our works, it is bj minimised matter chiefly tbat we are 

 undone. So injurious was tbe effect of this aureole tbat it was not 

 possible to obtain any pbotograi^bs of tbe corona at my observatory 

 near London. Tbis great diffraction aureole went far to defeat tbe 

 object for which Mr. Woods had gone to tbe Eiffel, but fortunately 

 tbe great advantage of being free from the effects of the lower 

 8000 feet of denser air told so strongly, that notwithstanding the 

 ever-present aureole Mr. Woods was able to obtain a number of 

 plates on which the corona shows itself with more or less distinct- 

 ness. [Three untouched photographic copies of the plates taken at 

 the Eiffel were shown upon the screen.] From the presence of the 

 aureole the negatives show less detail than we have every reason to 

 believe would have been the case if the sky had been as blue and clear 

 as in some former years. This circumstance makes great care neces- 

 sary in the discussion of these plates, and it would be premature to 

 say what information is to be obtained from them. 



[As an illustration of the differences of form which the corona has 

 assumed at different eclipses, photographs taken in 1871, 1878, 1882, 

 and 1883 were projected on the screen. Attention was called to the 

 equatorial extension seen in the photograph taken in 1878, and to 

 the suggestion which had been put forward that this peculiar cha- 

 racter was connected with the then comparative state of inactivity of 

 the sun's surface, at a period of minimum sun-spot action, especially 

 as an equatorial extension was observed in 1867.] 



It is now time that something should be said of the probable 

 nature of the corona. 



Six hypotheses have been suggested : — 



1. That the corona consists of a gaseous atmosphere resting upon 

 the sun's surface and carried rouud with it. 



2. That the corona is made up, wholly or in part, of gaseous and 

 finely divided matter which has been ejected from the sun, and is in 

 motion about the sun from the forces of ejection, of tlie sun's rotation, 

 and of gravity, — and possibly of a rejDulsion of some kind. 



3. That the corona resembles the rings of Saturn, and consists of 

 swarms of meteoric particles revolving with suf&cient velocity to 

 prevent their falling into the sun. 



4. That the corona is the appearance presented to us by the 

 unceasing falling into the sun of meteoric matter and the debris of 

 comets' tails. 



5. That the coronal rays and streamers are, at least in part, 

 meteoric streams strongly illuminated by their near ajDj^i'oacb to the 

 sun, neither revolving about nor falling into the sun, but permanent 

 in position and varying only in richness of meteoric matter, wdiich 

 are parts of eccentric comet orbits. This view has been supported by 



Vol. XI. (No. 79.) p 



