Quotation from: The Gods of Mars

Written by: Edgar Rice Burroughs

He smiled.

"You forget," he said, "that we are far below ground. The light
of the sun never penetrates here. There are no moons and no stars
reflected in the bosom of Omean. The phosphorescent light you
now see pervading this great subterranean vault emanates from the
rocks that form its dome; it is always thus upon Omean, just as
the billows are always as you see them--rolling, ever rolling over
a windless sea.