7 66 THE POPULAR SCIENCE MONTHLY. 



with the ceaseless and fearful activity of the sun's surface ; but we do 

 not know how far these actions, or the majority of them, may be in 

 the same electrical direction, or what other conditions there may be, 

 so as to cause the sun's surface to maintain a high electrical state, 

 whether positive or negative. A permanence of electric potential of 

 the same kind would seem to be required by the phenomena of comets' 

 tails. 



If such a state of high electric potential at the photosphere be 

 granted as is required to give rise to the repulsive force which the 

 phenomena of comets appear to indicate, then, considering the gaseous 

 irruptions and fiery storms of more than Titanic proportions which 

 are going on without ceasing at the solar surface, it does not go be- 

 yond what might well be, to suppose that portions of matter ejected 

 to great heights above the photosphere, and often with velocities not 

 far removed from that which would be necessary to set it free from 

 the sun's attraction, and very probably in the same electric state as 

 the photosphere, might so come under this assumed electric repulsion 

 as to be blown upward and to take on forms such as those seen in the 

 corona : the greatest distances to which the coronal streamers have 

 been traced are small as compared with the extent of the tails of com- 

 ets, but then the force of gravity which the electrical repulsion would 

 have to overcome near the sun would be enormously greater. 



It is in harmony with this view of things that the positions of 

 greatest coronal extension usually correspond with the spot-zones where 

 the solar activity is most fervent ; and also that a careful examination 

 of the structure of the corona suggests strongly that the forces to 

 which this complex and varying structure is due have their seat in the 

 sun. Matter repelled upward would rise with the smaller rotational 

 velocity of the photosphere, and lagging behind would give rise to 

 curved forms ; besides, the forces of irruption and subsequent electri- 

 cal repulsion might well vary in direction and not be always strictly 

 radial, and under such circumstances a structure of the character 

 which the corona presents might well result. The sub-permanency of 

 any great characteristic coronal forms, as, for example, the great rift 

 seen in the photographs of the Caroline Island eclipse, and also in those 

 taken in England a month before the eclipse and about a month after- 

 ward, must probably be explained by the maintenance for some time 

 of the conditions upon which the forms depend, and not by an unal- 

 tered identity of the coronal matter ; the permanency belonging to 

 the form only, and not to the matter, as in the case of a cloud over a 

 mountain-top or of a flame over the mouth of a volcano. If the 

 forces to which the corona is due have their seat in the sun, the corona 

 would probably rotate with it ; but if the corona is produced by con- 

 ditions external to the sun, then the corona might not be carried round 

 with the sun. 



We have seen that the corona consists probably of a sort of incan- 



