244 Mr. F. W. Dyson. 



" Abney " squares were printed on No. 6 when the plates were put 

 in their carriers the night before the eclipse. The exposure given was 

 15 s to the light of a standard candle at the distance of 5 feet. 



Of the eight photographs taken, the two by Burckhalter's method of 

 an occulting shutter, are failures. The failure is not due to any fault 

 in the method, but apparently is entirely owing to insufficient expo- 

 sure, the corona photographed on the plates not extending as far as 

 had been anticipated from previous eclipses. It seems probable that 

 with a clearer sky these would have been quite satisfactory. 



The other six photographs are excellent. The programme of expo- 

 sures, which was carefully arranged with the Astronomer Royal before 

 leaving England, has resulted in a well graduated series of photographs 

 from No. 1, which shows the prominences and a small amount of 

 corona to No. 5 in which the extension is shown to about 25' from 

 the Moon's limb. The polar plumes and the coronal streamers are 

 well brought out, as well as the remarkable detail of the inner corona. 

 Two features call for special note: (1) the polar streamers round the 

 Sun's north pole are not nearly so extensive as those round its south 

 pole ; (2) a very remarkable arch in the corona round the large 

 prominence at position angle 145 (measuring N.E.S.W.). Round this 

 prominence three separate arches are shown, one inside the other, their 

 radii being 1'% 2 /- 4, and 3''7 respectively. They have the appearance 

 of layers of clouds over an eruption. 



(2.) Small-scale Photographs to show Extension of the Corona. The 

 double camera was used in this eclipse exactly as at Ovar to carry a 

 Dallmeyer rapid rectilinear lens of 4 inches aperture and 34 inches 

 focus working at f/8 (lent by the Royal Astronomical Society), and a 

 " Unar " lens, by Ross, of 2'4 inches aperture and 12 inches focus, 

 working at//5. 



Eight plate-holders, each taking a pair of 16 cm. x 16 cm. plates, 

 were used during totality. The exposures, to avoid any possibility of 

 shake, were made by holding a cover in front of the object glasses. 



The mounting was exactly as at Ovar. 

 i The exposures were as follows : 



No. Duration. Plate, 



sees. 



1 5 Wratten and Wainwright Instantaneous. 



2 20 Ilford Empress. 



3 10 Imperial Ordinary. 



4 35 Imperial Special Rapid. 



5 20 Imperial Ordinary. 



6 35 Imperial Sovereign. 



7 5 Wratten and Wainwright Instantaneous. 



8 10 Imperial Ordinary. 



