Genesis 1:6

A firmament. — This is the Latin translation of the Greek word used by the translators of the Septuagint Version. Undoubtedly it means something solid; and such was the idea of the Greeks, and probably also of the Hebrews. As such it appears in the poetry of the Bible, where it is described as a mighty vault of molten glass (Job 37:18), upheld by the mountains as pillars (Job 26:11; 2 Samuel 22:8), and having doors and lattices through which the Deity pours forth abundance (Genesis 7:11; Psalms 78:23). Even in this “Hymn of Creation” we have poetry, but not expressed in vivid metaphors, but in sober and thoughtful language. Here, therefore, the word rendered “firmament” means an expanse. If, as geologists tell us, the earth at this stage was an incandescent mass, this expanse would be the ring of equilibrium, where the heat supplied from below was exactly equal to that given off by radiation into the cold ether above. And gradually this would sink lower and lower, until finally it reached the surface of the earth; and at this point the work of the second day would be complete.