St. Basil the Great, whom Aquinas probably quotes in this section, also preached on the Six Days of Creation in his Hexameron, which I'm skimming through right now:
If there is anything in this system which might appear probable to you, keep your admiration for the source of such perfect order, for the wisdom of God. Grand phenomena do not strike us the less when we have discovered something of their wonderful mechanism. Is it otherwise here?
If we were to wish to discover the essence of each of the beings which are offered for our contemplation, or come under our senses, we should be drawn away into long digressions, and the solution of the problem would require more words than I possess, to examine fully the matter. To spend time on such points would not prove to be to the edification of the Church.Words to the wise.