1911 Encyclopædia Britannica (1911)
“ Physical Features.—The Isthmus of Panama, coextensive with the republic, is the whole neck of land between the American continents; in another use the term " Isthmus of Panama " is applied to the narrow crossing between the cities of Colon and Panama, the other narrow crossings, further east, being the Isthmus of San Blas (31 m.) and the Isthmus of Darien (46 m.) . The use of the term " Isthmus of Panama " to include the whole country is becoming more common. The Caribbean coast-line is concave, the Pacific deeply convex. ”
