Anniversary Address. xxv. 



ECLIPSE. 



The total eclipse of the sun, visible throughout this part of the 

 world, which took place on the 6th of May last, had been looked forward 

 to by men of science with special attention, on account of the interest- 

 ing questions which it was expected to solve. 



The roseate protuberances, of the chromosphere which are seen 

 surrounding the limb of the sun during an eclipse were, by the 

 investigations which were made during and consequent upon the 

 eclipse of 1868, proved to be jets, composed almost exclusively of 

 incandescent hydrogen gas, to which I before referred in speaking 

 of the passage of the comet, bursting forth from the layers of vapour 

 which form the atmosphere to the sun. Amongst these vapours 

 spectrum analysis has detected sodium, magnesium, and calcium. 



Beyond this atmosphere, however, there is visible during a total 

 eclipse a magnificent silvery aureole, or luminous corona, which may 

 reach to a distance equal to an entire' radius of the moon's orbit. It 

 is not yet certain of what this corona is composed, and it is quite 

 possible that it may be a magnetic phenomenon analogous to the 

 aurora borealis. The remarkable association of the breaking-out of 

 sun-spots with the occurrence of violent magnetic storms on the sun's 

 surface gives support to this view. A marked instance of this 

 occurred on the 19th November last, when telegraphic communica- 

 tion was interfered with throughout the world, and an aurora was visible 

 over both hemispheres, associated with a very large sun-spot. 



To the corona again immense appendices have been observed. 

 Whether they are dependent on the coronal atmosphere, or are really 

 streams of meteorites circulating round the sun, was still uncertain ; 

 and this was one of the questions which it was hoped would be 

 decided by the observations taken during the eclipse of 1883, 

 especially as bearing on the remarkable theory lately put forth by Dr. 

 Siemens to explain the maintenance of the sun's energy, which sug- 

 gests that energy thrown off from the equatorial regions of the sun is 

 reabsorbed at the sun's poles, to be again re-formed into a source 

 of power. 



Prom the observations of the eclipse it was moreover expected that 

 information would be furnished respecting the small round spots which 

 have frequently been observed to appear and disappear in front of the 

 sun's orb. Can these be planets, revolving round the sun, but which 

 the illumination of our atmosphere, so bright in the neighbourhood 

 of the sun, conceals from us at other times? There are but two ways 

 in which the matter can be investigated — viz., the attentive study of 

 the solar surface (a work of great difficulty), and the examination 

 of the circumsolar region whilst an eclipse renders such examination 

 possible. As ordinary eclipses have only a duration of two minutes 



