No Barton in records. Must be a misspelling of Barlow Fisk, Nathaniel Sr's grandson. No Dr Martin Fisk but Dr Madison Fisk. Now Barlow Fisk had a son Martin Van Buren Fisk. The only one of Nathaniel Fisk's sons in Hilham, Overton Co in the 1850's was Nathaniel Fisk Jr. who moved to Missouri in the 1850's. A note says he was in Illinois in 1840. He was in the 1850 Census in Overton Co TN. He married Martha Goodpasture in HIlham, Overton Co TN in 1832. There is a gap with no children between 1834/5 & 1840 for Nathaniel Fisk Jr. Also the same for Dr Madison Fisk & Barlow Fisk. But no Martha Fisk that I can find in 1850 Census in TN. Certainly not in the households of Nathaniel Jr., Dr Madison Fisk, or Barlow Fisk .