lieport on the Solar Eclipse Expedition to 



51 



Three screws are provided in the base of the mirror cell for cor- 

 recting this error should any be found. 



Programme of Observations. The six slides were filled and intended 

 to be exposed as follows : 



Plate. 



Ilford " Empress." 

 Ditto, ditto. 

 Ditto, Special "Rapid. 

 Ditto, ditto. 

 Ditto, "Empress." 

 Ditto, ditto. 



Plates 2, 3, 4, 5 were backed with a solution of asphalfce in benzol 

 and had the Abney standard squares impressed on them. If the 

 rapidity of the Special Rapid be taken as twice that of the Empress 

 plates, the above programme gives a series of equivalent exposures 

 of 



2, 4, 8, 12, 24, 48 seconds. 



No exposures of less than 2 seconds were made, because it was 

 considered that the detail of the inner corona would be better shown 

 by the large scale pictures, of which at least four separate sets were 

 being taken by independent observers at other stations. 



The orientation of the corona was determined by the following 

 method : After the last exposure had been completed the clock was 

 stopped and the whole instrument was left untouched, with the slide 

 still in the camera, till night. The Abney lens was then uncovered 

 for about 2J hours, the mirror being left stationary, and a series of 

 star trails were thereby drawn across the plate. 



A recorder was employed whose duty was to note the exact time of 

 each exposure made during the eclipse. They were as follows : 



