on the west and north by the coasts of Viet-Nam and China
from latitude 10°N to Hong Kong;
on the east by the rhumb line from Hong Kong to the Port
of Sual (Luzon Island) and the west coasts of the Islands of Luzon,
Samar and Leyte to latitude 10°N;
on the south by the parallel of latitude 10°N.
Hong Kong and Sual are to be considered as being on the
boundary of the Seasonal Tropical Area and Summer Zone.