The northern boundary of the Tropical Zone is—
the parallel of latitude 13°N from the east coast of the
American continent to longitude 60°W, thence the rhumb line to
the point latitude 10°N, longitude 58°W, thence the parallel
of latitude 10°N to longitude 20°W, thence the meridian of
longitude 20°W to latitude 30°N and thence the parallel of
latitude 30°N to the west coast of Africa; from the east coast
of Africa the parallel of latitude 8°N to longitude 70°E,
thence the meridian of longitude 70°E to latitude 13°N, thence
the parallel of latitude 13°N to the west coast of India; thence
the south coast of India to latitude 10°30'N on the east coast
of India, thence the rhumb line to the point latitude 9°N, longitude
82°E, thence the meridian of longitude 82°E to latitude 8°N,
thence the parallel of latitude 8°N to the west coast of Malaysia,
thence the coast of South-East Asia to the east coast of Vietnam at
latitude 10°N, thence the parallel of latitude 10°N to longitude
145°E, thence the meridian of longitude 145°E to latitude
13°N and thence the parallel of latitude 13°N to the west
coast of the American continent.
Saigon is to be considered
as being on the boundary line of the Tropical Zone and the Seasonal
Tropical Area.