And God made the firmament,.... By a word speaking, commanding it into being, producing it out of the chaos, and spreading it in that vast space between the heaven of heavens and our earth .And divided the waters which were under the firmament from the waters which were above the firmament; the lower part of it, the atmosphere above, which are the clouds full of water, from whence rain descends upon the earth; and which divided between them and those that were left on the earth, and so under it, not yet gathered into one place; as it now does between the clouds of heaven and the waters of the sea.
Though Mr. Gregory is of opinion, that an abyss of waters above the most supreme orb is here meant; or a great deep between the heavens and the heaven of heavens, where, as in storehouses, the depth is laid up; and God has his treasures of snow, hail, and rain, and from whence he brought out the waters which drowned the world at the universal deluge.
Others suppose the waters above to be the crystalline heaven, which for its clearness resembles water; and which Milton calls the "crystalline ocean".And it was so: the firmament was accordingly made, and answered this purpose, to divide the waters below it from those above it; or "it was firm" , stable and durable; and so it has continued.
------and God made The firmament, expanse of liquid, pure, Transparent, elemental air, diffused In circuit to the uttermost convex Of this great round.------ Milton, Paradise Lost, B. 7. l. 263, &c. Notes and Observations, &c.
c. 23. p. 110, &c. Ibid. l. 291.