244 Mr. H. F. Newall on ErJ.ipse P-obJems. [Feb. 9, 



extent of the polarisation and of the brightness. The radially 

 polarised spectra not only extend both further from the moon's limb, 

 and also further into the ultra-violet, but also are considerably 

 stronger than the tangentially polarised spectra. 



I am also able to show a small region of one of the radially 

 polarised spectra on a very large scale, and side by side with it is the 

 corresponding bit of the solar spectrum. They are highly magnified 

 in both cases. In the solar spectrum we see the dark lines of calcium, 

 the H and K lines, and many other Fraunhofer lines. Now, if the 

 radially polarised spectrum is more intense because it contains re- 

 flected light, we may expect that the light reflected is similar to the 

 hght of the sun. The answer to any doubt on the point is got by 

 looking to see whether we find dark lines in the spectrum of the 

 corona corresponding with the dark lines in the solar spectrum. 



The conclusion that I come to from studying the original plates 

 very carefully, is that there arc no such dark lines, or that they are 

 far too feeble to account for the excess of the radial component over 

 the tangential. We are thus left with a need to find some other 

 acceptable cause of polarisation in the corona. In opposition to my 

 result is the result obtained by the American astronomer, Mr. Perrine, 

 in the Sumatra eclipse 1901, for his photograph showed the dark lines 

 without any doubt. Perrine's photograph was got with clouds in the 

 sky. Our Guelma records were got without any clouds in the sky. 

 It is rather difficult to say how much stress should be laid on the 

 clearness of the sky. 



I should like to complete my illustrations of the records got in 

 the 1905 eclipse by showing one of the valuable photographs obtained 

 by Mr. Dyson, at Sfax, viz. that in which the green corona line comes 

 out with remarkable intensity across patches of continuous spectrum, 

 in which no dark lines are seen. Mr. Dyson notes that in his photo- 

 graph there are two lines of unknown origin in the corona which 

 have not been observed before — two lines in the green part. It is 

 curious also to contrast the strength with which the green line 

 appears in the equatorial regions photographed by Mr. Dyson, with 

 the comparative feebleness with which it appears in my photographs 

 of the polar regions of the corona. 



I hope that I have not called too much upon your indulgence, 

 and that, though time has not allowed me to revert to my seedlings, 

 I have been able to show you that many valuable records have been 

 got during the three and a half minutes of the 1905 eclipse, which 

 will lead to interesting results when we have had time to study and 

 co-ordinate them. 



[H. F. N.] 



