12 
PROFESSOR J. NORMAN LOCKYER ON THE 
of this slit was adjusted so as to fall at the point where the photosphere would 
reappear after the end of totality. This “ dropping plate ” was intended to be 
exposed from as near as possible ten seconds before the end of totality, to 15 seconds 
after, the spectrum being moved slowly in the direction at right angles to the 
length of the spectrum. 
Fig. 2. 
The O-iucli Prismatic Camera. 
With this instrument tlie exposures were intended to be longer than with the 
G-inch, so that there might be a greater chance of obtaining impressions of the 
fainter coronal rings. The complete scheme of exposures was as follows :— 
