Then I had another look at the map Thomas Cochran made of the property after he acquired it from Denson's daughter. Sure enough, there's the "marshland of Thomas Cochran" extending far to the west of the rest of the grant. I had looked at it before and assumed that marsh was a separate property Cochran had acquired. Here's a link to view the map online.
I've been tearing my hair out trying to figure out how a property that Thomas Bacon purchased from Cochran's descendants could be bordered on the south and east by the Nappan River and on the west and south by Francis Smith. But this would make sense if the property was west of the highway.