Though the necessity of measuring the vertical flux of heat and water vapor, brought about by eddy movement in the lower atmosphere, has long been recognized, no direct method of determining these important quantities has previously appeared. The apparatus described here provides a continuous record, over a five-minute interval, of the detailed structure of temperature, vapor pressure, and total wind speed and its vertical component, of the air passing a fixed point. It is possible to derive the required fluxes from such records, and the method of analysis is discussed in some detail. Specimen records and measurements of the fluxes are presented. Abstract Though the necessity of measuring the vertical flux of heat and water vapor, brought about by eddy movement in the lower atmosphere, has long been recognized, no direct method of determining these important quantities has previously appeared. The apparatus described here provides a continuous record, over a five-minute interval, of the detailed structure of temperature, vapor pressure, and total wind speed and its vertical component, of the air passing a fixed point. It is possible to derive the required fluxes from such records, and the method of analysis is discussed in some detail. Specimen records and measurements of the fluxes are presented.