Page:Popular Science Monthly Volume 55.djvu/676

656 and thirty miles, and so on, as indicated by the curve. Now, it can readily be seen that this normal curve may also be considered the expectancy curve—if the wind has no effect. That is, if forty-eight per cent of the days of the year show a maximum velocity of the wind, between ten and twenty miles an hour, the law of probability would give us the same per cent of the crime for the year on such days if this meteorological condition were not effective. What we do find, however, is indicated by the other curves, and any increase of crime over expectancy may in this case be ascribed to the wind. We notice that for slight velocities (one to twenty miles an hour) the crime curves are below that of expectancy, but we can see that if the sum of all the per cents for any one curve is one hundred, and one is forced above the other at any part, there must be a corresponding deficiency at some other part. So we may, perhaps, with justice suppose that these mild velocities do not exert a positively quieting effect emotionally, but simply a less stimulating effect than the higher ones. For velocities of between twenty and thirty miles a marked effect is noticeable, and under those conditions the proportion of suicides to that expected is 37:29; velocities of from thirty to forty miles, 14:11; of forty to fifty miles, 7:2; of fifty to sixty miles, 0.4:2.6; of fifty to sixty miles, 0.2:2. The curve for murders shows the increase to be slightly less than for suicides, but the same general relation is preserved throughout. The value of such curves is, of course, somewhat proportional to the number of observations made and recorded, and we must confess that two hundred and sixty (suicides) and one hundred and eighty (murders) is a hardly sufficient number from which to deduce a definite law, but we can hardly doubt, even considering this somewhat limited number, that the wind is, in our problem, a factor of no mean importance.

—Fig. 3 is intended to show, in a similar manner, the relation between expectancy curves, based upon conditions of temperature, and the actual occurrence of the crimes in question. With this class of data, as well as that for the barometric