On the Corona of the Sun. 



127 



If we grant the existence of a high electric potential of the sun's 

 surface, we become possessed of a means of explanation of the chief 

 coronal phenomena, provided we accept the conclusion to which our 

 arguments have already led us, that the matter of the corona is of 

 solar origin. 



The photosphere is the seat of ceaseless convulsions and outbursts 

 of fiery matter. Storms of heated gas and incandescent hail rush 

 upwards, or in cylones, as many miles in a second as our hurricanes 

 move in an hour. Dante's and Milton's poetic imaginings of Hades 

 fall far below the common-place scenes at the solar surface. Is it then 

 going beyond what might well be, to suppose that some portions of the 

 photospheric matter, having an electric potential of the same kind as 

 that of the solar surface, from which they come, and ejected, as is 

 often the case, with velocities not far removed from that which would 

 be necessary to set them free from the sun's attraction, should come 

 under the action of a powerful electric repulsion, and so be carried 

 upwards, and from the sun ? 



If we take this view of things, we are able to accept the objective 

 reality of many of the very long coronal rays, which seem "to rest upon 

 sufficient testimony. At the eclipse of 1878, Professor Langley traced 

 the coronal matter to a distance of twelve solar diameters, and he 

 adds : "I feel great confidence in saying that (this distance) was bub 

 a portion of its extent."* Professor INewcomb traced this ray to 

 about the same distance, " six degrees from "the disk."f Such dis- 

 tances are small as compared with the extent of the tails of comets. 



This view of the corona is in harmony with the source of the 

 matter, and of the forces which the structure of the corona almost 

 irresistibly suggests, namely, that these have their seat in the sun. 

 We should expect, what we find to be the case, that there is usually 

 great coronal richness and extension over the spot zones where the 

 solar activity is most fervent. Matter blown upwards by an electrical 

 repulsion would rise with the smaller rotational velocity of the photo- 

 sphere from which it started, and would appear to lag behind in its 

 ascent, and so give rise to the curved rays, which are so common a 

 feature. We may well suppose that the forces of eruption and of 

 subsequent electrical repulsion would vary in different places, and 

 not be always strictly radial ; under such circumstances a structure, 

 similar to that which the corona presents, might arise. A force of 

 repulsion would also be present among the similarly electrified particles 

 of the corona, acting in all directions, and would cause these particles 

 to separate from each other, during their ascent from the sun ; the 

 amount of this diffusion would depend upon several factors, among 

 others, upon the original velocity of ascent, and upon the density 

 and the degree of electric potential of the repelled stuff. 



* Keport Total Eclipse, 1878, Washington, p. 208. f Idem, p. 104. 



