M. Quetelet, the head of the Observatory at Brussels, has paid great attention to the periodicity of weather-changes in Europe.  The result of his investigations is as follows: 

I. That there is always a “cold snap” between the 7th and 11th of January, during which ordinarily occurs the coldest day of the year.

II.  That from January 22 to March 1 there is, as we say in our vernacular, “a let-up” on the coldness of the temperature.  In France there is no ground-hog, or, if there is, he so generally sees no shadow upon Candlemas (February 2) that the three weeks succeeding it are called L’Ete de la Chandeleur.

III.  In April cold may be expected from the 9th to the 22d, and the Ice-Saints may prolong their influence to May 23, after which there is no more possibility of frosts in France, though within my memory June frosts have been twice known in Maryland and Virginia.  The prolonged frost in May is said to be produced by an understanding between the Ice-Saints and what is called in France La Lune Rousse,—­the Red Moon.

IV.  Though it needs no prophet to foretell hot weather from June 6 to June 23.  M, Quetelet’s observations point to June 13 and June 22 as days of exceptionally high temperature.

V. Between July 4 and July 8 comes the hottest day of the summer, which is not to be looked for in the dog-days, which are from July 21 to August 20.

VI.  July 25 distinguishes itself by being cool, and August 25 tempers ten days of heat which commonly begin on the 15th of August.

VII.  September 14 and September 30 are days when the thermometer may be expected to make a sudden fall.

VIII.  Cold weather may be looked for from October 20 to October 29, and from November 10 to November 19; but in the first ten days of November comes what we call Indian summer, and the French L’Ete des Morts,—­because it succeeds All-Souls’ Day,—­or L’Ete de Saint Martin.

M. Quetelet adds no observations on December, it being presumably a cold month everywhere.

M. Fourmet, of Lyons, has also made meteorological observations of the same nature in Southern France, and especially in the valley of the Rhone.  He says the lowest temperature in each month is as follows:  January 9 and 21.  February 3, 12, and 20.  March 5 and 21.  April 19.  May 12, 13, and 14.  June 8, 20, and 27.  July 12 and 25.  August 2, 12, and 24.  September 5, 15, and 30.  October 22.  November 5 and 17.  December 3 and 29.

M. Charles Sainte-Claire Deville has also been engaged in careful weather-calculations for many years, and has been in constant correspondence on the subject with the Academie des Sciences.  His theory is based on the existence of the three Ice-Saints in May, and he considers that a similar periodic influence may be traced in other months of the year.  He maintains that there are three days in every month, with an interval of about ten days between them, in which we may look for a fall of temperature, and that the weather gradually grows warmer during the interval that separates them.  His observations are only in part corroborated by those of M. Quetelet and M. Fourmet.