The spectroscope has revealed the fact that, broadly speaking, the sun
is composed of the same materials as the earth. Angstrom was the first
to map out all of the lines to be found in the solar spectrum. But
Rowland, of Baltimore, after having perfected the art of making true
gratings with equidistant lines ruled on metal for producing spectra,
then proceeded to make a map of the solar spectrum on a large scale.

In 1866 Lockyer[9] threw an image of the sun upon the slit of a
spectroscope, and was thus enabled to compare the spectrum of a spot
with that of the general solar surface. The observation proved the
darkness of a spot to be caused by increased absorption of light, not
only in the dark lines, which are widened, but over the entire
spectrum. In 1883 Young resolved this continuous obscurity into an
infinite number of fine lines, which have all been traced in a shadowy
way on to the general solar surface. Lockyer also detected
displacements of the spectrum lines in the spots, such as would be
produced by a rapid motion in the line of sight. It has been found
that both uprushes and downrushes occur, but there is no marked
predominance of either in a sun-spot. The velocity of motion thus
indicated in the line of sight sometimes appears to amount to 320
miles a second. But it must be remembered that pressure of a gas has
some effect in displacing the spectral lines. So we must go on,
collecting data, until a time comes when the meaning of all the facts
can be made clear.

_Total Solar Eclipses_.--During total solar eclipses the time is so
short, and the circumstances so impressive, that drawings of the
appearance could not always be trusted. The red prominences of jagged
form that are seen round the moon's edge, and the corona with its
streamers radiating or interlacing, have much detail that can hardly