W. A. Norton on the Corona in Eclipses 0/ Ike Sun. 13 



comet, because of a diminished gravitation toward the sun. 

 Upon our fundamental conception that the coronal matter is 

 essentially in the same physical condition as such cometic 

 matter, and subject to the action of the same solar forces, it 

 may well happen that some individual jets will proceed in con- 

 vex, and others in concave curves, according as the escapmg 

 matter is repelled or attracted by the sun. 



2. Observations on the physical constiiutwn of the corona with 

 the Spectroscope and Polariscope.—The results of the observations 

 made at the late eclipse, with the spectroscope and polariscope, 

 are strongly confirmatory of the truth of the theory ot the 

 corona under discussion. Professor Pickering m the Report of 

 his observations with a polariscope, says, " The form of polari- 

 scope used was that adopted by Arago in his expenmente on sky 

 polarization. It consists of a tube about twenty inches long 

 and two inches in diameter, one end of which is closed by a 

 double image prism of Iceland spar, and the other by a plate 

 of quartz. Looking through the former we see two images of 

 the latter, which when the light is polarized assumes com- 

 plementary tints. If, now, the corona was polarized m planes 

 passing through the center of the sun (as is generally admitted), 

 when viewed through the polariscope, in one image the upper 

 and lower parts should have appeared blue, and those on the 

 right and left yellow ; while in the second image these colors 

 would be reversed, the yellow being above and below, and the 

 blue on the sides. In reality the two images were precisely 

 alike, and both pure white, but one was on a blue and the 

 other on a yellow back-ground. From this we infer that the 

 corona was unpolarized, or, at least, that the polarization was 

 too slight to be perceptible." 



We may infer from this that the corona is either self lumi- 

 nous or shines by diffuse reflection ; since specular reflection 

 produces polarization.* . .„ j • • 



The testimony of the spectroscope is still more decisive. 

 Profs. Pickering, Harkness, and Young, agree that the spec- 

 trum from the light of the corona was a continuous one, or tree 

 from dark lines; but containing one or more bright lines The 

 absence of dark lines indicates that the corona did not shme 

 by the light of the photosphere, reflected either difiiisely or 

 specularly from ite substance ; since such light, after reflection 

 should, like the direct solar light, have given a spectrum with 

 the Fraunhofer lines. The presence of bnght lines, on the 

 other hand, is a direct indication that the corona was sell lumi- 

 nous ; and therefore that its light was the result either of com- 



♦The question whether the %ht from the corona is in any decree polanzP^^^ 



