THE ECLIPSE OF 1871. 119 



well defined; while the blue zone was faint and 

 indistinct. The green zone was well defined at the 

 summit, though less bright than at the base ; its form 

 was sensibly circular and its height about six or seven 

 minutes' (corresponding to a real depth of from 

 160,000 to 185,000 miles). 'The red zone exhibited 

 the same form, and approximately the same height as 

 the green ; but its light was weaker and less uniform. 

 These zones shone out upon a faintly illuminated 

 ground without any marked trace of colour. If the 

 corona contained rays of any other kind, their intensity 

 must have been so feeble that they were merged in the 

 general illumination of the field.' 



' Soon after the middle of the totality,' he proceeds, 

 4 there appeared on the sun's eastern edge a fine group 

 of prominences formed of jets, rather low, but very 

 bright, some rectilinear, others curved round the sun's 

 limb, and exhibiting the intricate deviations and all 

 the characters of prominences in the neighbourhood of 

 solar spots. The brightness and colour of these jets 

 were so vivid as to give them the appearance of fire- 

 works. The spaces between some of the jets were 

 perfectly dark, so that the red zone of the corona 

 appeared to be entirely wanting there.' (It will be 

 remembered that the red images of the prominences, 

 and the red image of the corona, were necessarily 

 accordant in position, since they were produced by the 

 same kind of light, the red hydrogen rays.) * Perhaps, 

 however, this was only the effect of contrast due to the 

 extraordinary brightness of the neighbouring jets. I 



