and as the throne of Christ was over this crystal firmament, it shows that, though he is in heaven, he sees all that is done on earth, and in his churches, and by his ministers; and the saints also see him by faith, and through the glass of the Gospel: it is only a crystal firmament that is between them,stretched forth over their heads above; that is, over the heads of the living creatures, as before; said to be stretched out, in allusion to its name, an expanse, as before observed.
Nat. Hit. l. 37. c.