This work undertakes the presentation of salient features of an encyclopedic subject in a more or less condensed fashion. The importance of the study of heating and illumination is thought to be its contribution to the history of culture as connected with the inventiveness displayed by man in the adaptation of the primary natural key force nearest to his needs in all the earlier stages of progress. The history also suggests the intellectual, esthetic, and religious reactions marking the several stages of culture gradually attained by man.