The tropical Low of September 14–15, 1904, is selected as a case for the study of a weak tropical Low intensifying as it moves to higher latitudes. By the use of barograms, thermograms, and autographic wind records, the storm track is reconstructed and hourly surface maps ara drawn. The barograms, thermograms, and wind records are combined on single charts for individual stations showing that the increase in winds is associated with the inflow of cold air. The central pressure of the Low is determined and found to decrease as the Low moves northward. Filling of the Low begins after it moves north of 39.5° N.