344 Sir Xoruiun 



In 1871 I used a 6-inch object glass, and distinctly observed marked 

 delicate thread-like filaments, reminding one of the structure of the 

 prominences, with mottling and nebulous indications here and there ; 

 some of these distinct markings were obvious enough to be seen till 

 some minutes after totality.* 



This year, with a perfect 4-inch Taylor lens and a high power, not 

 the slightest appearance of this structure was to be traced ; the corona 

 some 2' or 3' above the chromosphere was absolutely without any 

 detailed markings whatever. 



Lieut. Doughty duplicated and confirmed these observations with a 

 3f Cooke. Here, then, is established another well-marked difference 

 between maximum and minimum coronas. 



Tlie Coronagraplis. 



Four coronagraphs were employed of various apertures and focal 

 lengths. One, of 4 inches aperture and 16 feet focal length, was in 

 charge of Mr. Howard Payn, while the others were controlled by 

 officers of the ship. 



The results obtained are very satisfactory, those taken with the 

 long-focus instrument being especially good. In this case the image is 

 If inches in diameter, and the definition is perfect. The photograph 

 taken with an exposure of 5 seconds shows a great wealth of detail in 

 the inner corona and prominences ; the fine definition appears to be 

 due to the fact that a Taylor photo-visual lens was employed, bringing 

 the rays of various refrangibilities to the same focus. A long ex- 

 posure photograph, with the same instrument, is remarkable for the 

 perfect hardness of the moon's edge, notwithstanding the motion during 

 totality. 



The three photographs secured by Asst. Engineer Portch, R.N., 

 with the De la Rue lens of 4 inches aperture, give also sharp images 

 with much fine detail. 



Sandell triple-coated plates were used with this instrument. 



With the 6-inch Dallmeyer lens, two photographs on Sandell plates 

 were obtained by Dr. Martin, R.N., one being exposed for about half 

 a second, and another for 50 seconds. 



The longer exposure records the extensions to a greater distance 

 from the dark moon than any of the other photographs obtained, with 

 the exception of the one secured with the small-grating camera. 



This last-mentioned instrument consisted of a Zeiss anastigmatic 

 lens of 9 inches focal length, with a small Thorp grating mounted in 

 front of it. The exposure of the plate was 40 seconds during totality \ 

 the longest streamer in the N.E. quadrant extends to a distance of 4i 

 lunar diameters. 



* ' Solar Physics,' p. :<":>. 



