The rainfall of the Ohio Valley ?uctuated in clearly defined eight-year cycles during the seventy-two years from 1839 to 1910; The cycles in the Ohio Valley were congruent with those in the United States considered as a unit. The course of rainfall before 1839, when there were no meteorological records in the middle and western portions of the United States, may be a subject of dis pute, and one may have individual doubts as to the course of rainfall in the unrealized future. But the revelations of the existing record of eighty-three years describe a sequence of regular natural changes of such magnitude and of such economic importance that the observant explorer in quest of economic regularities will not ignore their suggestiveness. They supply a clue to the intricate economic disorder.