"Reefs growling in the surf like hidden tiger-fangs, sheer cliffs and giant waves breaking on them like the hammer of Ogun, until mountains trembled..." (p. 179)
Who is Ogun? Nowadays, we can instantly google.
Nantucket is an island in two oceans, one spatial, the other temporal or eternal. These literal and metaphorical oceans are never far apart in the text. Marian Alston is a sea traveler who has also been a time traveler. Poul Anderson links seafarers, spacefarers and timefarers near the end of "Ivory, And Apes, And Peacocks."
Those who travel into the prehistoric past enter a period when gods were seen as real:
"'...we shall have weapons of great power - like the Maruts of Indara Thunderer- or the sons of Teshub...Are your hands skilled to war, your hearts full of Agni's fire?'" (p. 184)
And, when the wanderer Denesh (Keith Denison) departs the camp of the Bakhri, King Thuliash says:
"'...I ask Indra the Thunderer that he bid his warrior Maruts watch over you for as far their range may reach...'"
-Poul Anderson, The Shield Of Time (New York, 1991), p. 278.
If human beings proliferate through many timelines, then so will their gods. In fact, combining once again the themes of ocean and gods, Alston thinks:
"...the Lord Jesus pity any fisherman out tonight in a Bronze Age coracle..." (On The Oceans..., p. 179)
Jesus has not been born, will not be born in this timeline, but we carry our gods within us.