thermochrosy

from The Century Dictionary.

• noun The property possessed by radiant heat of being composed, like light, of rays of different refrangibilities, varying in rate or degree of transmission through diathermic substances.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) The property possessed by heat of being composed, like light, of rays of different degrees of refrangibility, which are unequal in rate or degree of transmission through diathermic substances.