isotheral

If the surface of the Earth consisted of one and the same homogeneous fluid mass, or of strata of rock having the same color, density, smoothness, and power of absorbing heat from the solar rays, and of radiating it in a similar manner through the atmosphere, the isothermal, isotheral, and isochimenal lines would all be parallel to the equator.

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 Alexander von Humboldt 1814

Isochimenal and isotheral lines are the lines of equal winter and summer heat.

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 Alexander von Humboldt 1814

The lines which I have termed 'Isochimenal' and 'isotheral' (lines of equal winter and equal summer temperature) are by no means parallel with the

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 Alexander von Humboldt 1814

Since we have acquired a more accurate knowledge of the true relations of the distribution of heat on the surface of the earth, that is to say, of the inflections of isothermal and isotheral lines, and their unequal distance apart in the different eastern and western systems of temperature in Asia,

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 Alexander von Humboldt 1814

The nature of these inflections, the angles at which the isothermal, isotheral, or isochimenal lines intersect the parallels of latitude, their convexity or concavity with respect to the pole of the same hemisphere, are dependent on causes which more or less modify the temperature under different degrees of longitude.

COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 Alexander von Humboldt 1814