London Fog of January 11–12, 1925


THE accompanying curve (Fig. 1) indicates the variation in the quantity of suspended impurity in the air of Westminster during the recent fog. There was nothing very abnormal until the night of Saturday, January 10, when the suspended impurity, instead of gradually falling in the afternoon as it usually does, commenced to rise at about 5 P.M., reaching about 2 milligrams per cubic metre by 9 P.M. This level of impurity was maintained until midnight, when the normal fall occurred to a minimum of less than 0.5 milligram per cubic metre at 5–7 o'clock on Sunday morning. After this the impurity rose rapidly until it passed beyond the scale of the recording instrument at 3 o'clock on Sunday afternoon. It remained at this abnormally high level, which was more than 6.5 milligrams per cubic metre—probably approaching 10—until 7 P.M., when a gradual fall commenced, which was maintained fairly steadily until 5 o'clock on Monday morning, when the impurity was a little more than 0.5 milligram. The same rapid increase in impurity again began on Monday morning about 7 A.M., reaching a maximum of a little less than 4 milligrams per cubic metre at noon. This was maintained until 3 P.M., when there was a rapid fall until 6 P.M.

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OWENS, J. London Fog of January 11–12, 1925. Nature 115, 121 (1925).

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