﻿226 Prof. W. A. Norton on the Corona seen 



The grounds upon which I have maintained the auroral 

 origin of the corona in different publications are the following : 



1. The corona cannot be the permanent atmosphere of the 

 sun, shining by reflected light, since its outline is neither cir- 

 cular nor oval, but exceedingly irregular, and it extends out 

 from the sun many times further in some directions than in 

 others. The utmost that can reasonably be maintained is that 

 for a small portion of its outward extent, for which the grada- 

 tion of light is nearly uniform, it may possibly be a solar 

 atmosphere. 



2. The natural indications of the aspect of the corona are 

 that it is chiefly composed of separate masses of luminous 

 matter, of unequal brightness and length, radiating out from 

 different points of the sun's limb. The general radiated struc- 

 ture of the corona, and the great comparative outward extent 

 of the luminous radiations in certain directions, have attracted 

 the attention of the observers of all modern eclipses. Some 

 streamers have been seen to extend more than 1,000,000 miles 

 from the sun, while others did not extend to one quarter of this 

 distance. 



3. Reasoning analogically from the earth" to the sun, we 

 naturally conceive the body of the sun to be surrounded by a 

 permanent atmosphere. On the same grounds we should infer 

 that the space exterior to this atmosphere is pervaded, either 

 occasionally or permanently, by auroral streamers, similar to 

 those which at times shoot out many hundreds of miles into 

 space from the upper atmosphere of the earth. 



4. If the luminous radiations of the corona are in fact 

 auroral streamers, we must expect that they will not be per- 

 manent in their extent and position. Now it is well known 

 that such is the fact ; for the aspect of the corona has been 

 very different in different eclipses (e. g. eclipses of 1842, 1851, 

 1858, and 1860). It has even been maintained by some ob- 

 servers that the rays of the corona had a flickering lustre, and 

 varied in extent and position during the short period of a single 

 eclipse. 



5. Admitting, as we must, the actual radiated [structure of 

 the corona, its individual streamers, or luminous radiations, 

 may be conceived either to be permanently connected with the 

 sun, or to be composed of luminous matter actually streaming 

 away from the sun, to an indefinite distance, into space. If we 

 ■adopt the former idea, we virtually admit that a permanent 

 vaporous atmosphere of sensible density extends from the body 

 of the sun to a distance greater than the sun's diameter — a posi- 

 tion that cannot with any plausibility be maintained *. In sup- 



* According to the recent spectroscopic determinations of Lockyer and 



