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



columns ; that by electric discharges along these columns their 

 substance becomes dispersed and in part projected into space, 

 and that this process, wherever occurring, may, by a continued 

 dissipation of a portion of the photospheric matter at that 

 locality, eventuate in the formation of a visible spot on the disk ; 

 that the photospheric matter thus discharged into space is in 

 that peculiar condition recognized in cometic matter in which it 

 becomes subject to a repulsive action from the sun (or else to a 

 diminished attractive action, as occurred to a certain extent in 

 the case of Donates comet, and in that of 1861), and in the act 

 of flowing away is visible in solar eclipses as the streamers of the 

 corona, and at more remote distances as the zodiacal light ; that 

 these solar emanations furnish the matter of terrestrial auroras, 

 and, when descending in copious showers into the earth's atmo- 

 sphere and developing electric currents and disturbing the 

 magnetic condition of the earth, are the determining cause of 

 all the phenomena of "magnetic storms." The apparent struc- 

 ture and variability of the corona, and, as we shall soon see, the 

 most characteristic features of its form, the form, position, and 

 variability of the zodiacal light, the coincidence of the periods of 

 the sun's spots with the periods of terrestrial auroras and with 

 those of the perturbations of the magnetic needle, all accord 

 with this general theory. I have also endeavoured to show, in 

 my papers on the variations of the magnetic elements, that these 

 variations are such as should naturally result from the electric 

 currents in the upper atmosphere (or what may be called the 

 photosphere of the earth) that would ensue from the reception 

 of the supposed impulsive waves and material emanations pro- 

 ceeding from the sun. (See Silliman's Journal, II. vol. xix. 

 March and July, 1855). 



If it indeed be true that, from the fundamental conception of 

 material emanations from the sun, similar to those which we 

 know to take place from the head of a comet under the influence 

 of the sun, a connected series of phenomena may be theoretically 

 deduced which have their actual counterparts in nature, it must 

 be conceded that there is a high probability that this conception 

 is founded in truth, and furnishes the true explanation of the 

 varied phenomena observed. 



Results of Observations on the Corona made at the Total Eclipse 

 of August 7 , 1869. 



The observations made on the Corona on the occasion of the 

 eclipse of 1869, have furnished several striking confirmations of 

 the theory that it is an auroral phenomenon. 



1. The observed form and structure of the corona. — I will first 

 duce the results of my own observations. These were made 



