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In agricultural research as well as in applied climatology as a whole, there is an increasing demand for portable meteorological field equipment capable of recording continuously more environmental factors than the conventional hygro-thermograph. The spot climate recorder described can register dry bulb, wet bulb, soil, and black globe temperatures, and wind direction and velocity on either daily or weekly charts, whichever is best for the climate survey. If desired, all these elements can be registered on one chart, but a set of two recorders has been found to be no more expensive and gives the economic advantage of making each useable separately. This is desirable for instance when a network of wind registering stations is needed (including 1 temperature each) but the complete record of moisture, radiation, etc. is sufficient at one station. The wind-recording circuits are designed for low-current drain on a 6-volt storage battery. Rather than draw on this battery to provide aspiration for the dry and wet-bulb thermometers, the wind velocity record is used to determine at which few hours the wet-bulb record may be unreliable.

The objectives, means, and some of the results of intensive studies of the thermal aspects of microclimatological environment are discussed. The proposed Table 1 of weather types is believed in general to combine rather effectively the European classification, depending on air mass, and the American description by cloud cover. The latter is the more specific for insolation, but the former is most significant for nocturnal heat rates, for moisture, and for air “quality.” The special instrumentation described has been developed in studies of heat transfer from animals and plants, particularly for measuring conduction and radiation. Such electric sensing elements seem to have use in the overall measurement of agricultural climatic environment. The recording potentiometers needed for the micro studies made possible the automatic recording of all the regular weather‐station observations described. It is hoped that discussion will lead to some general agreement on minimum instrumentation. Any such agreement would encourage the establishment of many more environment stations and constitute an important step from qualitative toward quantitative experiments. Examples of the usefulness of the instrumentation are described and a heat balance between solar and sky radiation and the ground is discussed. With adequate understanding of heat balance, we believe that agricultural research findings at one station can be extended to other areas of somewhat different climate.

Despite the advances in the statistical theory of turbulence, the PRANDTL [see 1 of “References” at end of paper] concept of mixing‐length still affords the most convenient method of evaluating momentum‐transfer from velocity‐profiles in turbulent flow. In symmetrical conduits, eddy‐diffusivity is known directly from the BOUSSINESQ quotient of shear‐stress and velocity‐gradient. Hence mixing‐length is not essential for the expression of eddy‐diffusivity in pipe‐flow, but is convenient when the distribution of shear‐stress is not known, as in most flow‐problems in meteorology and hydrology.