与观者的眼睛相平,模棱两可,处于危险中,立即
, the boundary line between Pennsylvania and Maryland, as run before the Revolution (1764-1767) by two English astronomers named Charles Mason and Jeremiah Dixon. In an extended sense, the line between the free and the slave States. {On the line}, on a level with the eye of the spectator; -- said of a picture, as hung in an exhibition of pictures.