A few of the lines show a double reversal, the dark absorption line being greatly increased in breadth and showing a bright emission line in its centre.
The helium formations do not reach the sun's limb, and it is another puzzling detail that the spectrum of the disk shows no absorption line of anything like an intensity to correspond with the emission line of helium in the chromosphere.
The lines are broadened (as was already known), the intensity of emission is much increased, but some are weakened and some strengthened, nor is the amount of broadening the same for all lines, nor is it always symmetrical, being sometimes greater on the red side; but besides the effect of unsymmetrical broadening, every line is displaced towards the red; different lines again behave differently, and they may be arranged somewhat roughly in a few groups according to their behaviour; reversals are also effected, and the reversed line does not always correspond with the most intense part of the emission line.
Kirchhoff's second law A low-density gas will radiate an emission-line spectrum with an underlying emission continuum.
These coronagraphs produce images of the " emission line corona.
