Quotation from: General Science

Written by: Bertha M. Clark

What seems perhaps the most unexpected thing, is that the temperature,
as indicated by a sensitive thermometer, continues to rise if the
thermometer is moved just beyond the red light of the spectrum. There
actually seems to be more heat beyond the red than in the red, but if
the thermometer is moved too far away, the temperature again falls.
Later we shall see what this means.