Translation
Then ELOHIM said, “Come into being, oh beaten surface
Go to footnote numberbetween the waters, to divide the interval between the waters and the waters.
Paraphrase
Then THE CREATOR AND OWNER OF ALL THINGS said, “Oh vast, strong, thin, arched surface that I see in my mind, I command you to become a physical reality, so you can divide the space between one bunch of water and the other bunch of water.”
Footnotes
1: “beaten surface”
The word used here comes from a root meaning “to beat.” It was usually used of precious metals that were beaten with a hammer for covering objects with a thin layer of gold – called gilding. Because it was “something solid that was extended by beating it until it was thin,” it came to mean such things as “expanse, extended surface, firm, solid.” Hence the King James rendering of “firmament.” The surface could be flat, curved, or shaped. Here it is obviously curved.
The use of this word in this context has given headaches to translators for a very long time.
To us it seems silly to think of the sky as something solid. However, I think the sky was described as being solid because whatever was up there did not come crashing down upon us; the things up there stayed up there and the sky was, in a manner of speaking, holding them in place. Thus, among the various emphases possible, the focus here is that it is a layer that is strong and expansive.