256 



Mr. E. W. Maunder. 



somewhat out of the centre of the plate in all three of the photo- 

 graphs ; and owing partly to shake in the instrument, and partly to 

 the excessive atmospheric disturbance, which under the high magni- 

 fication employed was very apparent, the definition is poor in each 

 case. 



No. 1. The corona is shown to a height of about 1 minute of arc. 

 The image is faint. 



No. 2. The corona is shown to a height of about 3 minutes of arc. 

 The image is fairly dense. 



No. 3. The corona is shown to a height of about 2 minutes of arc. 

 The image is faint and flat. 



The Mauritius photoheliograph was focussed by repeated photographs 

 of the Sun, taken during the fortnight preceding the eclipse. 



(2.) Photographs on the 2'i-inch Scale. 



These were taken with the object-glass of the Dallmeyer photo- 

 heliograph No. 5, belonging to the Royal Observatory, Greenwich 

 and which, like that of the Mauritius photoheliograph, had an 

 aperture of 4 inches and a focal length of 5 feet used in connection 

 with a concave telephoto lens by Dallmeyer, of 3 inches aperture and 

 12 inches focal length. The instrument thus constructed has been 

 referred to for convenience as the " Greenwich coronagraph," and 

 was about 7^ feet in actual length, with an equivalent focal length 

 of nearly 21 feet. It was furnished with ten plate-holders to take 12 

 by 10-inch plates, and it was proposed to take seven photographs 

 during totality. 



These photographs were taken by myself, Colour-Sergeant-Major 

 Wade exposing at the object-glass of the instrument by the signal 

 bells as follows : 



After the ground glass had been inserted for the observation of third 

 contact, and had been removed again, the aperture was diminished to 

 half an inch, and the clock of the coelostat stopped and three photo- 



