Summary.—Fig. 1 shows at a glance no generally prevailing meteorological conditions to which can be ascribed, with any degree of certainty, the monthly variations of crime.
Fig. 2 shows that high velocities of wind seem to increase to a marked extent the tendency to crime. For the highest velocities increasing the probability twenty times (two thousand per cent).
Fig. 3 shows that high temperatures seem to have the same effect, that of between 90° and 100° increasing the probability one hundred per cent.
Fig. 4 fails to show that barometric changes are accompanied by any marked excesses in crime.
Fig. 5 shows that low conditions of relative humidity are attended with very marked excesses, those below thirty increasing the probability of suicides eleven times (eleven hundred per cent).
Fig. 6 fails to show that the character of the day has any considerable effect.
Considering briefly, in conclusion, the results of the foregoing study, and comparing them with a somewhat similar one for children,[E] we may safely conclude that the tendency to homicide varies with those meteorological conditions which bring about an emotional state necessitating a considerable discharge of motor stimulus. The same conditions which bring about irritability and unruliness on the part of the child accompany suicidal tendencies.
This supposition is upheld by the fact that suicide is less common in the colder climates, where the metabolic processes are slow, and in the torrid zone, where the heat produces a general depletion of energy for motor discharge, than in the temperate regions, where the climate is exhilarating. The study, from the social standpoint, too, leads us to the same conclusion. The excess of crime in the social whirlpools of our great cities is convincing, and especially the careful study made by Morselli of the prevalence of suicide in the different countries of Europe, interpreted in the light of what we know of their social conditions.
Yet, in considering the facts disclosed by the present paper, we must not dogmatically assert that each is of the importance that the figures indicate. In fact, it seems evident from a careful study of the sheets, which show all the conditions together for the same day—a thing impossible with the charts illustrating this paper—that the various conditions for the day mutually react and interact upon one another, certain combinations seemingly resulting in a re-enforcement of the tendency to crime, while certain others inhibit it. Space forbids any full discussion of this phase of the problem in the present paper, but it very probably will be made the subject of some future study.
Author's Note.—The above paper was written more than a year ago. Since that time the work of comparing the prevalence of crime with the meteorological conditions has been carried on upon a much larger scale in the city of New York. An immensely greater number of data have served to corroborate the earlier conclusions arrived at in this Denver study, only in minor points—and those directly traceable to the very different climates—proving at all in opposition to them.—New York, July, 1899.