6 W. A. Norton on the Corona in Eclipses of the Sun. 



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

 very different in diflFerent 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 luster, and 

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



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- 

 port of the other hypothesis we have the well established fact 

 that some form of luminous matter, belonging to cometary 

 bodies, when it comes under a certain degree of influence fi-om 

 the sun, is projected or in some manner detached from the 

 nuclei of these bodies, and repelled from the sun, and under 

 the operation of the solar repulsion urged away from them to 

 an indefinite distance, forming the luminous trains by which 

 they are attended. (See the author s papers on Donati's Comet 

 published in this Journal, Jan. and May," 1860, and July, 1861 ; 

 and the discussion of the Dynamical Condition of the Head of 

 a Comet in the No. for Jan., 1859). To suppose that the rays 

 of the corona are actual radiations of luminous matter, is onlv 

 ! that £ 

 ubject 



perceive the sun to exert" upon a portion of the matter of 

 comets. The luminosity of such radiations may be ascribed 

 either to a reflection of the sun's light, or to electric discharges. 

 Upon this question we shall see important evidence was ob- 

 tained at the total eclipse of Aug. 7, 1869. 



6. If we adopt the auroral theory of the corona, and at the 

 same time admit that the auroral streamers are actual emana- 

 tions of luminous matter, the following consequences may be 

 expected to follow. 



(1.) A portion of the auroral matter emitted from the sun 

 should fall upon the earth's atmosphere, and may furnish the 

 substance of terrestrial auroras, for which no terrestrial origin 

 has yet been detected. 



(2.) Upon this view of the possible origin of terrestrial 

 auroras, the close correspondence that has been detected be- 

 tween the periods of the sun's spots and of auroras, should sub- 

 * According to the recent spectroscopic determinations of Lockyer and Frank- 

 land, the solar atmosphere must be of exceeding tenuity in therftcHnn ^f tl,« rn«»- 

 colored protuberances just above the general surface of the c 



