With a quick fix of punctuation, it's much easier to understand your question. You are asking about the chapter of Chesapeake entitled "Voyage Seven: 1811." It is a unique voyage of the novel because it doesn't have any of the main characters in it (which include many families from the Chesapeake Bay area! The traveler on voyage seven is a farmer named Applegarth who becomes entranced with his own assumption of how the Chesapeake Bay area of Pennsylvania was formed: ice. Note the following quotation:
He saw clearly one fact: that the ice sheet must have contained within it an enormous quantity of water, and when the ice finally melted, that water must have formed a gigantic river, parent to the present Susquehanna. And that river, nothing else, had reamed out the Chesapeake Bay and deposited the silt which had become, in time, the Eastern Shore.
The farmer of voyage seven became obsessed with tracing the river to its source with only a hunter from the area as a guide. When he found the source, it was a bit anticlimactic, with there being a meadow and only a "slow accumulation of moisture." It wasn't the huge ice flow he was expecting. Still, Applegarth wrote down his travels in a book called To the Ice age which contained (instead of lots of scientific facts) lots of observation of the Chesapeake Bay Area.