Horsford continued his research, finding evidence of Norse era dams, canals, piers, and settlements in Watertown, and a Norse era fortification in Waltham. Horsford oversaw the re-creation of the fortification: a stone tower in the Norumbega region of the Charles River (right). The tower is located on Norumbega Road, near the intersection with River Road.
Horsford hypothesized an extensive series of North American settlements, with a population of nearly 10,000 people, which thrived for three centuries. He proposed that the economic basis for the settlements was mazer wood, the round burls (left) that grow on the sides of trees. These burls are valuable for the ease with which they can be worked into bowls, cups, and similar round objects. Horsford hypothesized that the burls were harvested in the forests and floated down to the Charles in canals, for which he claimed to have found physical evidence.
interesting.....but probably not true, i found it on the internet