Relationships between smoke concentration and visibility, wind direction, wind speed, and temperature stratification are discussed with some references to previous investigations which have related these factors. The paper deals with smoke pollution such as exists in an industrial city, rather than with the effluent from a point- or line-source drifting over an area of constant surface roughness. The review includes some of the findings of the writers, who have made a number of correlations between Weather Bureau meteorological data and Davidson's New York City smoke data of 1939–40. The best of these correlations resulted when the wind direction and wind speed were considered hour by hour for each day, and when a straight-line regression formula was fitted to the data. It is brought out that isobaric curvature, as shown on the weather maps, seems to be a significant factor in the smoke-spreading problem.
* Now with Hq, Air Weather Service, Washington, D. C.
‡ Now with Division of Tuberculosis, U. S. Public Health Service, Washington, D. C.