In this study energy-exchange processes and climatic influences are examined in relation to thermal comfort and work efficiency as exemplified in a schoolroom situation. The investigation tests fundamental hypotheses on meterotropisms and optimal thermal environments and demonstrates how daily variations within atmospheric environments are considerably more important than had been previously suspected. It also describes the experimental use of a variety of microclimatic instruments and thermal indices in conjunction with psychological tests of continuous mental performance. The Atmospheric Environment treats a complex problem from a broad multi-disciplinary standpoint and is of particular interest to climatologists, psychologists, teachers and educational administrators, heating and ventilating engineers, and to all concerned with environmental management. (Department of Geography Research Publications 8).