CIRCLE, the rendering of the difficult Heb. term, חוּג, H2553, variant חָג, which apparently means “circular edge” and can thus mean “horizon.” It is tr. “circle” only in Isaiah 40:22, but elsewhere as “compass” (Prov 8:27) or “compassed” (Job 26:10 KJV). The RSV consistently renders “circle.” The precise determination of the OT notion of cosmology is difficult to pursue as the Bible gives only the faintest clues and it is unwise to extend those literary phrases by what is known from other Sem. peoples. Certainly the text in no wise assumes a spherical earth, nor does it completely exclude such an insight. All the usage of the term indicates is that the horizon where the sea meets the sky was known by observation to be curved, and that it was upon this arc that Jehovah set the limits of the seas.
International Standard Bible Encyclopedia (1915)
sur’-k’-l: Is used with reference to the vault of the heavens (hugh) in Isa 40:22, and in a similar sense in 13:2 ( margin), "circle of stars" (kuklos astron). It is also used in the sense of surrounding territory, as in the expression "circle of Jordan" (Ge 13:10 the Revised Version, margin).
See also CICCAR; ASTRONOMY, sec. III, 1.