232 Mr. H. F. Newall. 



(iii) For 4-i minutes, starting at the count " Thirty " after the 

 beginning of totality and ending at the count " Sixty, five minutes 

 gone." 



(iv) For 2 seconds, when I gave the signal " Now " at the end of 

 totality. 



Lieutenant Briggs carried out the programme with admirable 

 precision. 



Result. All four photographs are of value. The first serves for 

 determination of the scale of the spectrum and shows that the focussing 

 was very successful. The second and fourth photographs show both 

 bright and dark lines, as was intended ; the second is a weak negative, 

 but is full of interesting details ; the fourth is quite strong, teeming 

 with bright crescents, of which more than ninety have been counted 

 between A 4308 and A 4405. Many of the crescents are bright through- 

 out their whole length ; many are reversed in the middle ; some of 

 the bright crescents are accompaned by dark crescents on either side ; 

 others have a dark crescent only on one side or the other ; all varieties 

 seem to be represented. 



The third photograph is not very strong but it shows marked con- 

 tinuous spectrum, with the blue coronal ring distinctly though not easily 

 visible. The edges are ill-defined, in marked contrast with the sharp 

 prominence-tips that serve to mark out the positions of the H y and 

 Hs chromospheric rings. 



The radial extension of the blue coronal ring is about 3', but there 

 is no sign of radial structure. 



Two determinations of the wave-length of the light forming the blue 

 ring give the values 4231 '4 and 4231 '9, if the wave-lengths ascribed to 

 the dark H y and HS lines may be adopted for the bright hydrogen 

 prominences. 



The dispersion is about 5' 14 tenth-metres to a millimetre, and the 

 scale of the ring is such that its diameter corresponds to 65 tenth- 

 metres. The conditions are thus favourable for the detection of 

 coronal rings. No ring except that at 4231 has been with certainty 

 detected between H v and H$. 



17. Visual Objective-grating Spectroscope. 



An objective grating spectroscope was used as in India, in 1898,* 

 for visual observations of the green coronal ring, with a view to 

 (i) repeating the search made during the Indian eclipse for fine radial 

 streamers, (ii) comparing the distribution of light in the green ring 

 with that in the blue ring near A 4231, of which I hoped to get a 

 photograph with a photographic objective grating camera. 



A plane grating by Eowland, 14,438 lines to the inch, on a ruled 



* ' Roy. Soc. Proc.,' vol. 64, p. 57; ' Monthly Notices, Eoy. Astro. Soc.,' vol. 58, 

 App., p. [57]. 



