There is present no satisfactory theory for the wet and dry bulb hygrometer in moving air and these experiments were started with idea of getting more information about the effect of the rate of evaporation and the shape of the covered bulb on the lowering of temperature. So far in this investigation only the cylindrical shape has been used. Only a section of the cylinder is covered with moistened muslin and with constant air velocity and humidity, the rates of cooling are compared when the covered section makes different angles with the air stream
