THE SUN'S CORONA AND HIS SPOTS. 17 



sun. Therefore probably what Bruhns calls the base of the 

 corona was in reality only the prominence region, and the inner 

 corona was that which he describes as varying in breadth or 

 height from nearly one-half to a quarter of a degree that is 

 from about 800,000 to about 400,000 miles. De la Rue gives a 

 somewhat similar general description of the corona seen 'in 

 1860. He remarks that it was extremely bright near the 

 moon's body, and of a silvery whiteness. The picture of 

 the corona by Feilitsch (given at p. 343 of my book on the 

 Sun) accords with these descriptions. 



On the whole, the eclipse of 1860 affords evidence 

 according well with the theory we have been considering, 

 except as regards the brightness and the colour of the corona, 

 which correspond more closely with what was observed in 

 July, 1878, with the lustre and colour of the corona in 1870 

 and 1871. In this respect, it is singular that the eclipse 

 of 1867. which occurred (see preceding note) when the 

 sun spots were fewer in number, presented a decided contrast 

 to that of 1860, the contrast being, however, precisely the 

 reverse of that which our theory would require, if the colour 

 and brightness of the corona be considered essential features 

 of any law of association. 



Herr Grosch. describing the corona of 1867, says, 

 * There appeared around the moon a reddish glimmering 

 light similar to that of the aurora, and almost simultaneously 

 with this (I mean very shortly after it) the corona.' It is 

 clear, however, from what follows, that the reddish light was 

 what is now commonly called the inner corona, which last 

 July, when the sun was in almost exactly the same condi- 

 tion as regards the spots, was pearly white and intensely 

 bright. ' This reddish glimmer/ he proceeds, * which 

 surrounded the moon with a border of the breadth of at 

 most five minutes' (about 140,000 miles) ' was not sharply 

 bounded in any part, but was extremely diffused and less 

 distinct in the neighbourhood of the poles.' Of the outer 

 corona he remarks that * its apparent height amounted to 



c 



