The seventh voyage described in Chesapeake is unique because it is the only voyage that does not feature any of the major families from near Patamoke as principal characters. The Paxmore family helps to finance the voyage, but the traveler is a tenant farmer named Thomas Applegarth.
During the winter of 1811, when there wasn't a great deal for farmers to do, Applegarth became fascinated with the geological history of the eastern Pennsylvania - Chesapeake Bay area. Based on reading and thinking and studying maps of the eastern United States and speculating with Elizabeth Paxmore, Applegarth came to an understanding of how the topography of the area was formed.
Ice!...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.
Applegarth undertook to observe the remaining signs of this process by tracing the Susquehanna River north to its headwaters. He traveled by water and by land, alone much of the time but with a local hunter accompanying him into the wooded fields of New York to search for the river's origin. On May 4, 1811,
he came to the ultimate source of the river. It was a kind of meadow in which nothing happened...merely the slow accumulation of moisture from many unseen and unimportant sources
Applegarth recorded the story of his travels and his conclusions in a book entitled To the Ice Age, which came to be recognized as the perceptively written observations of a scientist with no formal training but a great appreciation of the powers of observation and the unity of all the forces working together to shape the territory he had explored.