In the course of research by Battelle on the fundamentals of flow of mixtures of air and pulverized coal, for Bituminous Coal Research, Inc., a meter has been developed which measures the rate of flow of both constituents. The meter depends on a unique property of the mixture when passing through a sharp-edged rubber-faced orifice to which coal does not adhere. It was found that the presence of finely divided coal in the air stream has very little effect on the accuracy with which the orifice indicates the flow of the air component, whereas a flow nozzle placed in series with the orifice measures the total of the air plus coal. Thus the simultaneous use of the two elements provides a means for determining the amount of coal flowing. This paper describes the development of the meter, presents data on its performance, and gives the details of practical application. The rate of coal flow is measured with an accuracy of plus or minus 5 per cent for coal-air ratios ranging from 0.5 to 1.4, and for coal sizes ranging from 75 to 92 per cent through 200 mesh, after allowance has been made for the small effects of these variables. The meter has been used successfully in the laboratory in vertical and horizontal pipe lines from ¾ to 4 in. diam and it is believed to be applicable to larger lines.