But as the climate and vegetation become arctic at 12,000 feet, it will be as well to confine my observations to the flora of 7000 to 10,000 feet; of the mean temperature, namely, between 53 degrees and 43 degrees, the isothermal lines corresponding to which embrace, on the surface of the globe, at the level of the sea, a space varying in different meridians from three to twelve degrees of latitude.
"Himalayan Journals V2."
J. D. Hooker
It would do so if the steam remained or was maintained at a uniform temperature; hence it is called the isothermal curve, or curve of same temperature.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose
The arrangement of the isothermal lines, not only on neighbouring continents, but even throughout Europe, would be changed.
"Essays: Scientific, Political, & Speculative, Vol. I"
Herbert Spencer