"Had the Gods really carved out a strait at the Creation in order that Gaius Valerius Gratillonius could have a day's worth of feeling like the boy he once was?" (pp. 60-61)
Two features of this question are of interest. First, Gratillonius thinks of "Gods," not of "God," in relation to the Creation. Secondly, he really thinks that Earth was created as it is now with the Channel in place between Britannia and Gallia.
Of course, not only have the continents moved and changed since the formation of the Earth but also the Channel separating the island of Britain from the continent of Europe had existed for only a few thousand years before the lifetime of Gratillonius. We know that we live in a world of geographical, geological and cosmic changes but that knowledge has been won in the millennium and a half separating us from Gratillonius. The Andersons take their readers inside the mind of a man of the declining Roman Empire.