'Arch' in the Bible

And over the heads of the living beings there was the form of an arch, looking like ice, stretched out over their heads on high.

Under the arch their wings were straight, one stretched out to another: every one had two wings covering their bodies on this side and two covering their bodies on that side.

And there was a voice from the top of the arch which was over their heads: when they came to rest they let down their wings.

And on the top of the arch which was over their heads was the form of a king's seat, like a sapphire stone; and on the form of the seat was the form of a man seated on it on high.

Then looking, I saw that on the arch which was over the head of the winged ones there was seen over them what seemed like a sapphire stone, having the form of a king's seat.