Dexter, in an elaborate study of the relationship of conduct to the weather, shows that in the United States assaults present the maximum of frequency in April and October, with a decrease during the summer and the winter. "The unusual and interesting fact demonstrated here with a certainty that cannot be doubted is," he concludes, "that the unseasonably hot days of spring and autumn are the pugnacious ones, even though the actual heat be much less than for summer. We might infer from this that conditions of heat, up to a certain extent, are vitalizing, while, at the same time, irritating, but above that limit, heat is so devitalizing in its effects as to leave hardly energy enough to carry on a fight." (E.G. Dexter, _Conduct and the Weather_, 1899, pp. 63 _et seq._)
It is not impossible that the phenomena of seasonal periodicity in crimes may possess a real significance in relation to sexual periodicity. If, as is possible, the occurrence of spring and autumn climaxes of criminal activity is due less to any special exciting causes at these seasons than to the depressing influences of heat and cold in summer and winter, it may appear reasonable to ask whether the spring and autumn climaxes of sexual activity are not really also largely due to a like depressing influence of extreme temperatures at the other two seasons.
Not only is there periodicity in criminal conduct, but even within the normal range of good and bad conduct seasonal periodicity may still be traced. In his _Physical and Industrial Training of Criminals_, H.D. Wey gives charts of the conduct of seven prisoners during several years, as shown by the marks received. These charts show that there is a very decided tendency to good behavior during summer and winter, while in spring (February, March, and April) and in autumn (August, September and October) there are very marked falls to bad conduct, each individual tending to adhere to a conduct-curve of his own. Wey does not himself appear to have noticed this seasonal periodicity. Marro, however, has investigated this question in Turin on a large scale and reaches results not very dissimilar from those shown by Wey's figures in New York. He noted the months in which over 4,000 punishments were inflicted on prisoners for assaults, insults, threatening language, etc., and shows the annual curve in Tavola VI of his _Caratteri dei Delinquenti_. There is a marked and isolated climax in May; a still more sudden rise leads to the chief maximum of punishment in August; and from the minimum in October there is rapid ascent during the two following months to a climax much inferior to that of May.