364 Rev. A. L Cortie [Feb. 26, 



outstanding features of the spectroscopic records obtained at this 

 eclipse. In addition, both parties of observers employed a comparison 

 spectrum for the first time in eclipse observations, the Greenwich 

 observers using the spark spectram, and the Stonyhurst observers the 

 arc spectram of iron. 



The co-ordination of the various phenomena observed on the 

 sun's surface, or in the surrounding envelopes, is of primary im- 

 portance in the advance of knowledge of solar physics. Sun-spots are 

 undoubtedly the chief foci of activity in the manifestations of 

 energy displayed by facul^, flocculi, and eruptive prominences. The 

 relation, therefore, which may exist between sun-spots, or areas of 

 sun-spot activity, and the streamers of the sun's corona is a subject 

 worthy of investigation. 



The concordance between the general aspect of the sun's corona 

 and the curve of sun-spot activity has been well established. At 

 times of maximum sun-spot activity the corona extends all round 

 the sun in irregular masses. At minimum there are two long wings 

 disposed equatorially, generally in the form of a wind- vane, with open 

 spaces at the poles filled with delicate filmy rays. At periods inter- 

 mediate between maximum and minimum there are a number of 

 bright streamers, which are superposed upon the equatorial wings, 

 which have now extended both northwards and southwards. It 

 has not unfrequently been asserted,* since sun-spots are confined 

 within zones some 30^ north and south of the equator, while pro- 

 minences, which are more active at sun-spot maxima, are found in all 

 latitudes, and even at the poles, that the solar corona reflects rather 

 the variations of the curve of prominence activity than those of the 

 sun-spot curve. Hence the conclusion has been drawn that the 

 streamers of the corona emanate from regions of prominence activity. 

 But there seems to be very little, if any, direct evidence of this from 

 eclipse photographs. Whatever direct evidence we possess of the 

 connexion between prominences and the solar corona points to the 

 formation of a system of beautiful interlacing arches in the lower 

 portions of the corona, immediately over the prominences. This is 

 shown in a striking manner, for instance, in the photographs ob- 

 tained by Professor Schaeberle in the eclipse of 1893, and in my own 

 photographs of that of 1905. 



If the streamers are supposed to emanate from regions of sun- 

 spot activity, it is not difficult to explain the general aspect of the 

 corona. As a preliminary, it must be borne in mind that we are 

 viewing the streamers, which really exist in space in three dimen- 

 sions, projected around a seemingly flat disk in two dimensions. The 

 sun-spot zones have a limiting latitude of about 30° north and south 

 of the solar equator, and at times of minimum have a mean latitude 

 which is much lower. This explains the two main wings which are 



* e.g. Proceedings of the R.I., xx. p. 352. 



