152 Dr. A. Schuster and Capt. W. de W. Abney. [Apr. 19, 



1. An ordinary camera with lens of 4-inch apertnre, and focal 

 length of 5 feet 3 inches. 



2. A prismatic camera, that is, a camera with prism in front of the 

 lens, or, in other words, a spectroscope without collimator. The 

 refracting angle of the prism was 60°; its face 3 inches sqnare. The 

 camera had a corrected lens with a focal length of 20 inches in the 

 yellow. The plate to be exposed was sensitive in the red as well as 

 in the blue. 



3. A photographic spectroscope, with one prism of a refracting angle 

 of 62°, and a length of collimator and camera of 9 inches. 



The general appearance of the corona seemed to the naked eye (of 

 Dr. Schuster) not to have been strikingly different to that of the two 

 previous eclipses, either in brilliancy or extension, but the photographs 

 reveal very essential differences. 



Some time observations were made at the first and last contact, and 

 the length of the eclipse was measured to be 74 seconds. 



The second part of the paper gives the results of a careful investi- 

 gation of all the photographs obtained. 



Three photographs of the corona itself with different times of 

 exposure, viz., 3, 11, and 23 seconds, show a gradual increase in the 

 extension of the corona. Care had been taken to fix, by means of a 

 wire stretched across the camera, the position of the corona, and it is 

 believed that the orientation is accurate within probably a quarter of 

 a degree. The photographs show the prominences very well, and 

 confirm the distinction which has been drawn between the inner and 

 the outer corona. The shape of the corona was very irregular. A close 

 connexion between the outline of the corona and the state of the 

 snn's surface is placed beyond doubt. During the time of minimum 

 sun-spots a great extension in a direction approximately coincident 

 both with the ecliptic and with the sun's equator is observed, and we 

 can generally trace a distinct line of symmetry nearly agreeing with the 

 sun's «ixis of rotation. In addition to the long equatorial rifts, short 

 but sharp rifts appear near the sun's poles. At times of great solar 

 activity these rifts are not seen, nor is there any symmetry whatever 

 in the general outline of the corona. 



During the present eclipse the photographic impression of one of 

 the rifts reached to a distance of 1*4 solar diameters away from the 

 sun's limb. As regards form and general appearance of the streamers 

 two points deserve special notice. One is the remarkable curvature 

 of some of the coronal rays. The rays seem in many cases to start 

 almost tangentially from the sun's limb ; sometimes they are wider 

 near the sun's limb, contracting as their distance increases ; some of 

 the rifts, however, spread out in a fan-like fashion. The second point 

 to be noticed is the transparency of the streamers : in two instances at 

 least we can trace structural details through the luminous streamers. 



