FIRMAMENT The great vault or expanse of sky that separates the upper and lower waters. The firmament was created by God on the second day to separate the "waters from the waters" (Gen. 1:6-7). One use of "heaven" in the Bible is to refer to the ceiling or canopy of the earth. Heaven in this sense is also referred to as the firmament or sky (Gen. 1:8). Into this expanse, God set the sun, moon, and stars (Gen. 1:14-18).
The word "firmament" comes from the Latin word firmamentum in the Vulgate. There it is used to translate the Greek word stereoma in the Septuagint rendering of Genesis 1:6-7. The original Hebrew word raqiac denotes a strip of hammered out metal. God spreads out (verbal form of raqia ) the sky (Job 37:18). At times the use of the word connotes the idea of extension or expansion--thus the expanse of the heavens at creation.
In Genesis 1:6 the firmament separates the mass of waters and divides them into layers. The firmament is mentioned nine times in Genesis, the Psalms, Ezekiel, and Daniel. It is described as bright, transparent like crystal, revealing the handiwork of God, and signifying His seat of power (Pss. 19:1; 150:1; Ezek. 1:22; Dan. 12:3).
Some scholars argue that the Hebrews had a primitive cosmology where the firmament was visualized as a rigid, solid dome--a celestial dam (Gen. 7:11; 2 Sam. 22:8; Job. 26:8; 37:18; Prov. 8:28; Mal. 3:10). Above the firmament flowed the heavenly waters. The firmament was punctuated by grilles or sluices, "windows of heaven" through which rain was released. Others argue that such interpretations are unsound, in that they confuse poetic and figurative language with literal prose. Others say Israel's inspired writers used language of experience and appearance rather than language of precise scientific description.
See Heavens. Paul Robertson
Also, Jack, have you forgotten the Book of Enoch excerpts I posted on BioGenesis that clearly showed the concept of a dome with gates through which rain and snow were dumped to earth and through whick lightening was lowered and raised on chains and wheels?