iSyi.] The Eclipse of Last December. 247 



were well known to all familiar with the history of physical 

 astronomy. I take it that the fruits of the expeditions may 

 be thus summarised : — In the first place the corona has at 

 length been photographed, so that its peculiarities may be 

 studied at our leisure without fear of mistakes arising from 

 inexact delineation. Secondly, the connection between the 

 ring-formed and the radiated corona has been demonstrated 

 by the photographic and other evidence showing how the 

 height of the bright inner corona corresponds with that 

 of the outer corona. (This is a most important discovery.) 

 Thirdly, the fact that one of the lines of the corona 

 spectrum is identical with Kirchhoff' s 1474, a line seen in 

 the spectrum of our own aurora, has been abundantly 

 demonstrated. Fourthly, the region in which the Fraiinhofer 

 lines have their origin has been ascertained and shown to 

 be an atmospheric envelope (which may be some two or 

 three hundred miles deep) lying immediately above the 

 photosphere. Fifthly, the theory that the sierra is of the 

 nature of an atmosphere has been invalidated, and the 

 earlier opinion (which Professor Respighi had supported on 

 the evidence of his spectroscopic observations) has been 

 confirmed if not demonstrated, — the view, viz., that the 

 sierra consists of multitudes of the rosy prominences 

 resembling the large ones in all other attributes except 

 size. 



I shall, not venture to theorise in this place respecting the 

 real nature of the corona ; for the present we may remain 

 satisfied by having learned beyond all question its real 

 position in space, and something of its physical constitution. 

 There are problems of extreme interest concerning it which 

 still await solution. There are difficulties, also, which must by 

 no means be overlooked if we would explain its phenomena 

 aright. To future observation and research these problems 

 and difficulties may not unsafely be relegated. 



