THE ECLIPSE OF 1871. 117 



zones, with the tints of the chromatic images of the 

 corona. My attention was mainly directed to the 

 forms of the prominences, and I was able to determine 

 that the fundamental form, the skeleton or trunk, and 

 the principal branches, were faithfully reproduced or 

 indicated in all the images, their extent being, however, 

 greatest in the red, and diminishing successively in the 

 other colours down to the indigo images, in which the 

 trunk alone was reproduced. In none of the pro- 

 minences thus compared was I able to distinguish in 

 the yellow image parts or branches not contained in 

 the red image. 1 Meanwhile the coloured images of 

 the corona became continually more strongly marked, 

 one in the red corresponding with the red line of 

 hydrogen, another in the green ' (corresponding with 

 Professor Young's green line), ' and a third in the 

 blue, probably corresponding with the blue line of 

 hydrogen.' 



1 The interest of the question whether such differences would be 

 perceived resides in the fact that the red, green, and indigo images are 

 all due to hydrogen, but the yellow to another element, present in the 

 prominences ; and Respighi hoped to ascertain whether this element 

 extended beyond, or not so far, as the hydrogen. For our own part, 

 we are disposed to place very litttle reliance on some of the facts 

 observed in this particular part of Respighi's work. With the red and 

 yellow images shining in full splendour, he would naturally be unable 

 to see the fainter parts of the indigo images ; but these darker images 

 are probably at least as extensive as they are certainly as well-defined 

 as the others. For Secchi, in studying the prominences by the spec- 

 troscopic method, selects the indigo images for the purpose, because he 

 has found that c&teris paribus the indigo images appear the most com- 

 plete. In Respighi's work other things were not equal. Similar re- 

 marks apply to the apparently inferior extension of the blue green 

 image of the inner corona. 



