Firmament? Much speculation on the "firmament".

This naive Genesis author thought that the sky, since it provided water, was like rivers and oceans. The perfectly logical conclusion would be that there’s a mass of water in the sky that needs to be held up.

Thus it follows that a solid body, a firmament, would be necessary to support this oceanic reservoir. Ergo, a transparent sphere above and surrounding the earth (they thought it was flat) that divided the waters which were under the firmament from the waters which were above the firmament.