Isotherm
ISOTHERM (Gr. Zeros, equal, and 9epw, heat), a line upon a map connecting places where the temperature is the same at sea-level on the earth's surface. These isothermal lines will be found to vary from- month to month over the two hemispheres, or over local areas, during summer and winter, and their position is modified by continental or oceanic conditions.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
