Total Eclipse of the Sun, 1901, May 18. 



243 



in the centre f inch in diameter, through which a spindle, mounted on 

 the back of the plate carrier, was passed. On this spindle the screen 

 was fixed in the dark room after the plate had been put in the carrier.' 



Occulting Shutter for Photographs of Corona by Burckhalter's Method. 



The figures against the dotted lines show the effective exposures at different 

 distances from the Sun's centre. 



During the exposure, the observer turned a small handle about once 

 a second, which, by a suitable train of wheels, caused the screen to 

 turn about eight times a second. The apparatus appears to work 

 perfectly smoothly, as the limb of the Moon is sharply defined on the 

 photographs taken. 



The eight slides were exposed as below, the exposures being made 

 at the object glass by Dr. Nimmo : 



A ninth plate was taken at 1 o'clock, local time, on which two 

 exposures were made (the driving clock being stopped for two minutes 

 between) for determination of the orientation of the plates. 



8 2 



