our meteorological phenomena, the fact that the periods of greater and less energy indicated by spots on its disk have a well-marked relationship to the temperature and rainfall is not surprising. While there are many fluctuations for which no solution is attempted, it suffices if we are able to point out well-defined maxima and minima periodical fluctuations which conform to each other within small limitations.
The proof does not rest alone upon the Detroit observations. Though the rainfall at Milwaukee and Cleveland differs, often considerably, in times and amount, from the Detroit record, we find a close conformity in the periods. In fact, there is almost identity in the periodic means of all the elements contained in the table.
TABLE No. II.
Maximum and Minimum Periods of Sun-Spots, Temperature, Rainfall, and Water-Levels, 1834-1887.