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second slit; and as successive sections of the
sun’s image in the equatoreal enter the ap-
paratus, so are these sections successively
thrown in their proper place on the pho-
tographic plate, always in K light. By us-
˜
ing a high dispersion the faculA which give
off K light can be correctly photographed,
not only at the sun’s edge, but all over his
surface. The actual mechanical method of
470
