44 
POPULAE SCIENCE EEYIEW. 
coloured envelope, — the sierra or chromatosphere, — which may 
he regarded as one of the solar atmospheres. We are waiting at 
present for further information on this very point from the 
observers of the eclipse of December 1 2 ; hut beyond all ques- 
tion very clear information was obtained during the Mediter- 
ranean eclipse of December 1870. Spectroscopy and polari- 
scopv did not avail to tell us all we wished to know respecting 
the corona ; and through unfavourable weather photography 
failed in doing what it would assuredly have done had the sky 
at Syracuse cleared round the sun only two minutes earlier. 
In the last eleven seconds of totality, however, one good picture 
of the corona (the first ever taken) was obtained by Mr. 
Brothers ; and that picture, besides showing what Mr. Brothers’s 
method was capable of effecting, gave evidence of the utmost 
importance in relation to the physical condition of the sun. 
Combined with the spectroscopic charting of the prominences 
by Mr. Seabroke (during the day of the eclipse, but not during 
totality), and confirmed by the photograph taken in Spain 
by Mr. Willard, as well as by the direct observation of the 
inner corona by Professor Watson, this photograph indicates an 
association between the prominences, the inner corona and the 
outer radiated corona, which must be accounted for in any 
theory respecting the condition of the matter surrounding the 
sun’s globe. Wherever the prominences were large and re- 
markable, there the inner corona was brightest and extended 
farthest from the sun, and opposite those same regions lay 
the great radial beams of the outer corona. Combining these re- 
lations with the well-known fact that the solar spot-zone is the 
region in which the prominences have their greatest activity, 
we see that we are on the traces of a law relating to the whole 
economy of the great ruling luminary of our planetary system. 
Now the study of the solar spots, on the one hand, presents 
difficulties so serious in their nature that we can scarcely 
wonder at the fact that hitherto no consistent theory has been 
put forward in explanation of their phenomena ; and, on the 
other hand, the study of the solar corona is simply the most 
difficult of all the subjects of investigation which the student of 
solar physics can present to himself. Holding a place between 
the phenomena of the spots and those presented by the corona, 
and associating together these classes of phenomena, are the 
phenomena presented by the prominences; and these can for- 
tunately be studied in a systematic and (all things considered) 
a satisfactory manner. So long as the prominences could be 
studied only during eclipses, it was almost hopeless to look 
to them for information respecting the difficult problems of 
solar physics ; but so soon as a method was devised for exa- 
mining their features when the sun is not eclipsed, the whole 
