Calorific rays

from The Collaborative International Dictionary of English v.0.48

Calorific \Cal`o*rif"ic\, a. [L. calorificus; calor heat +
   facere to make; cf. F. calorifique.]
   Possessing the quality of producing heat; heating.
   [1913 Webster]

   {Calorific rays}, the invisible, heating rays which emanate
      from the sun, and from burning and heated bodies.
      [1913 Webster]