 While serving as Bishop of Tirunelveli (alongside Edward Sargent), Caldwell (who was not a trained archaeologist) did much original research on the history of Tirunelveli.He studied palm leaf manuscripts and Sangam literature in his search, and made several excavations, finding the foundations of ancient buildings, sepulchral urns and coins with the fish emblem of the Pandyan Kingdom.This work resulted in his book "A Political and General History of the District of Tinnevely" (1881), published by the Government of the Madras Presidency.