THE annual report for the year ending March 31, 1940, on the Investigation of Atmospheric Pollution, which would normally be issued by the Department of Scientific and Industrial Research, has been replaced by a summary prepared for the information of the co–operating bodies. From this it appears that the deposit over the whole of Great Britain, as represented by the deposit gauges, has decreased. The highest total deposit measured for the year (395 tons per square mile) was in Manchester, while the lowest measured (57 tons per square mile) was at Loggerheads, Shropshire; both places, however, show smaller deposits than in the previous year. There were only three complete sets of results with automatic filters: Cardiff, Coventry and Stoke–on–Trent. These are not sufficient to provide a basis for comparison with the previous year. The average monthly suspended impurity does, however, show interesting characteristics, notably maxima, in January 1940, which it will be remembered was unusually cold. This increase in suspended impurity was no doubt due to an increase in all forms of domestic heating during the cold period despite the shortage of fuel in some districts. All three places show a sharp increase in suspended impurity in October, followed by a minimum in November, although the average temperature for that month was lower than the average for the past fifty years or so. It may be that the continuation of Summer Time until November 20, 1939, and the restriction on the combustion of fuel imposed by the fuel rationing scheme may be responsible to some extent for these minima in November.