great thinkers have left on record their own emotional flights and depressions under different meteorological conditions. But most of us need to take no other word for the fact than our own. In all the vigor of perfect health such influence may hardly be recognized, but when the vital powers are depleted by the exhausting effects of a long nervous or physical strain, then this phase of the cosmical environment is sure to make itself felt. Then come the days when everything goes wrong. The groundwork of forgotten quarrels is remembered, uneasy questions arise with regard to the future; one gets tired of life. And how much of all this can be attributed to an east wind or a leaden sky—in other words, to weather effects? In order to answer this question we must define our use of the term 'weather effects.' From the standpoint of our present study we should include within the category of weather effects any marked inequality in the occurrence of suicide which may be found to bear a fixed relation to the fluctuations of what we call weather. We conclude that a fixed relation between a given weather state and an unusual prevalence of suicide is causal and not accidental. This is based upon an inductive study of large numbers of data, and is as valid as such studies can well be.
The problem, then, consists in discovering these fixed relations. In order to do this with exactness, the meteorologist's analysis of weather must be taken. To him a given weather state is a complex and not a simple phenomenon. He reads its temperature, its barometer, its humidity, its wind velocity, its sunshine or shade, and its precipitation, and it is only to the synthesis of these conditions that he applies the term weather. For the purpose of our present study it is not enough to say that the weather is fine, or disagreeable, or muggy, for those terms mean one thing to one person and something very different to another, so it has been necessary to make use of a definite meteorological nomenclature which is recognized the world over. The study is in no sense an attempt to account for suicide, but for the irregularity of its occurrence. Man always has sought and perhaps always will seek self-destruction as the relief for sorrow, fancied or real, and the basal reason for this is not to be found in the weather. We would not argue that the weather drives people to suicide save in very exceptional cases, but, on the strength of what follows, that under some weather states other things are peculiarly liable to drive people to the act. In other words, that some meteorological conditions so affect the mental state, so influence the emotional balance, that ordinarily endurable things become unendurable, and life seems no longer worth the living.
This problem, which seems to show a causal nexus between the weather and the mental state of the suicide, is a comparison of the occurrence of suicide under different meteorological conditions, with the normal prevalence of those conditions, noting the excess or deficiency.
