1891.] Frof. A. Schuster on Becent Total Solar Eclijpses. 273 



WEEKLY EVENING MEETING, 



Friday, February 13, 1891. 



' William Huggins, Esq. D.C.L. LL*D. F.E.S. Vice-President, 



in the Chair. 



Professor Arthur Schuster, Ph.D. F.R.S. 



Becent Total Solar Eclipses. 



Successful observations of solar eclipses began with the invention of 

 the spectroscope. Though valuable results had been persoDally 

 obtained, especially by De la Eue in 1860, the bulk of the observa- 

 tions made before 1868 are of a kind which at present can be carried on 

 without the help of an eclipse. The steady progress of eclipse work 

 of late years is not, however, altogether due to the spectroscope, but 

 in great part to the science of photography, which of late years has 

 advanced with rapid strides. In order to judge of the amount of 

 information actually obtained, it is well to bear in mind the short 

 time which has been at our disposal ; the aggregate time during which 

 eclipse observations have been carried on since the construction of the 

 spectroscope hardly exceeds half an hour. 



The primary object of an eclipse expedition is to investigate the 

 regions of space which are in the vicinity of the sun, and we may 

 hope thereby ultimately to obtain important information concerning 

 the constitution of interstellar space. 



The lecturer explained the peculiar difficulties of eclipse observa- 

 tions, the preparations for which often have to be conducted under 

 great disadvantages, especially when, as happened in the West Indian 

 eclipse of 1886, the weather is of such an unsettled character that 

 up to the last minute of the eclipse it was uncertain whether anything 

 could be seen at all. 



Photographs of the solar corona as observed in different eclipses 

 were thrown on the screen, and attention was drawn to the great 

 differences in its general outline and character. Two types of corona 

 may be distinguished ; one of them principally appearing at a time of 

 sunspot maximum, while the other is chiefly seen when there are few 

 spots on the luminary. 



The corona of sunspot minimum is characterised by long streamers 

 spreading chiefly in directions which are not much inclined to the 

 solar equator. In addition to these extensions, curved lines are 

 noticed which seem to converge to two points on the solar surface 

 which are not far removed from the solar poles. If a line is drawn 

 through the two points of convergence, the corona is roughly 



