7.  “Let the waters bring forth the moving creatures that have life, and fowl that may fly above the earth in the open firmament of heaven.”  They received the command to fly above the earth because earth provides them with nourishment.  “In the firmament of heaven,” that is to say, as we have said before, in that part of the air called οὐρανός, heaven, cf. note on p. 70. from the word ὁρᾶν, which means to see; The Greek word στερέωμα, from στερεός, strong, is traceable to the root star, to spread out, and so indirectly associated with the connotation of the Hebrew rakia. called firmament, because the air which extends over our heads, compared to the æther, has greater density, and is thickened by the vapours which exhale from the earth.  You have then heaven adorned, earth beautified, the sea peopled with its own creatures, the air filled with birds which scour it in every direction.  Studious listener, think of all these creations which God has drawn out of nothing, think of all those which my speech has left out, to avoid tediousness, and not to exceed my limits; recognise everywhere the wisdom of God; never cease to wonder, and, through every creature, to glorify the Creator.