Bible Dictionaries
Firmament

Watson's Biblical & Theological Dictionary

It is said, Genesis 1:7 , that God made the firmament in the midst of the waters, to separate the inferior from the superior. The word used on this occasion properly signifies expansion, or something expanded. This expansion is properly the atmosphere, which encompasses the globe on all sides, and separates the water in the clouds from that on the earth.

Bibliography Information
Watson, Richard. Entry for 'Firmament'. Richard Watson's Biblical & Theological Dictionary. https://www.studylight.org/​dictionaries/​eng/​wtd/​f/firmament.html. 1831-2.