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which together form a chromosphere line; in this combination of 
are images we may expect a quite different distribution of the 
light than would be found in an image, formed either by mono- 
chromatic light or by one simple ray group, such as a more or 
less rarefied gas would show us in its emission lines. 
Let Z (fig. 2) be a portion of the moon’s edge at the instant of 
the second or third contact of a total eclipse. We may now consider 
the compound light, arising from a small column Za of the chro- 
mosphere, dispersed into a horizontal spectrum parallel to the line 
PP'. In order to obtain more easily an idea of the share which 
the various rays contribute to the light distribution in the band, we 
separate the various rays from one another and represent on distinct 
lines PP, QQ, RR .... those parts of the spectrum, where 
chromosphere light is found of wave-lengths equal respectively to 
A, hE DAE 20, ete! 
The point O may indicate the place, where the moon’s edge would 
be seen if absolutely monochromatic light of wave-length À appeared 
on its left. 
The rays of wave-length 4 are, however, completely absorbed, so 
that nothing need be represented on the line P P’. 
On the line QQ we find first the light of wave-length A — 0, 
which projects the sharp edge of the moon at « and reaches (with 
decreasing intensity) from there to @, and secondly the light of 
wave-length A + 0, which reaches from a’ to a. 
In the same way we find on RR' the rays A—20 and A+ 20, 
corresponding respectively to the sections 5/3 and 5'/?'; on SS the 
rays A— 36 and à +30 at the sections cy and c'y', etc. 
Because the sections aa, a'a', b/?, b' f'... represent the width 
of the chromosphere rings corresponding to the various sorts of rays, 
we have considered them proportional to the lengths aj ag, aj ag’, 
bj bo, by' b's of fig. 1. Hence the extremities a, 7,... and @',/?,... 
etc. lie on two curves, whose shape is closely related to that 
of the dispersion curve. The share which all intermediate waves bear 
in the light distribution is thus shown, if we only notice that for 
each kind of light the intensity decreases from right to left. This 
is represented by shading in the upper part of fig. 3. Finally to 
obtain the light distribution in the chromosphere line, we only need 
suppose that the figure is compressed in the vertical direction and 
that thus the light intensities are added together. The resulting 
intensity is then found to be approximately distributed as is shown 
by the shading in the spectrum given below. Hence a double line 
is produced, each of the components of which shades off gradually 
