590 
MR, J. NORMAN LOCKYER ON THE 
spectrum, when a slitless spectroscope is employed. Attention was drawn to this in 
the preliminary report,* and it was stated that the broad ill-defined ring, a little more 
refrangible than D 3 in some of the African photographs, as well as a less conspicuous 
one in the blue, and possibly even another in the violet, has its origin in the continuous 
Fig. 13. 
Illustrating clitferent depths of chromosphere photographed with one exposure. 
Fig. 14, 
Appearance of continuous spectrum photographed on an isochromalic plate with a ring slit. 
spectrum of the corona acting on a plate, w 7 hich has one maximum of sensitiveness for 
the yellow rays and one or more maxima in the blue and violet. Experiments with 
ring slits, illuminated by a source of light giving a continuous spectrum, have confirmed 
this explanation. The photograph reproduced in fig. 14 was taken on an isochromatic 
plate wdtli the 6-inch prismatic camera, temporarily provided with a 3^-inch collimator 
in which the slit was replaced by a positive picture of the corona. A bull’s-eve lamp 
* ‘ Phil. Trans.,’ 1894, vol. 185 A, p. 714. 
