In one passage God is said to have "founded his vault ('aghuddah) upon the earth" (Am 9:6). It is not quite certain whether this dome or vault refers to the earth itself, or to the heavens arched above it.
The latter is the usual interpretation, but in either case the reference is rather to the strength of the structure than to its form; the word implying something that is firmly bound together and hence, an arch or dome because of its stability.
See also ASTRONOMY, sec. III, 2.