Between the black
veins over the disk, also, there rise domes and columns of the
liquid fire, some hundreds of miles in diameter, spreading and
sinking at from five to twenty miles a second. The surface of the
sun--how much more the interior !--is an appalling cauldron of
incandescent matter from pole to pole. Every yard of the surface
is a hundred times as intense as the open furnace of a Titanic.
From the depths and from the surface of this fiery ocean, as, on
a small scale, from the surface of the tropical sea, the vapours
rise high into the extensive atmosphere, discharge some of their
heat into space, and sink back, cooler and heavier, upon the
disk.
This is a star in its yellow age, as are Capella and Arcturus and
other stars. The red stars carry the story further, as we should
expect. The heavier lines in their spectrum indicate more
absorption of light, and tell us that the vapours are thickening
about the globe; while compounds like titanium oxide make their
appearance, announcing a fall of temperature. Below these, again,
is a group of dark red or "carbon" stars, in which the process is
carried further. Thick, broad, dark lines in the red end of the
spectrum announce the appearance of compounds of carbon, and a
still lower fall of temperature.
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