While thus showing that the number of trials for murder is the best test of the prevalence of this offence, it is not meant that the test is in all respects indisputable.  At most it is merely approximate.  One obstacle in the way of its entire accuracy consists in the circumstance that the proportion of persons tried, as compared with the amount of crime committed, is in no two countries precisely the same.  In France, for instance, more murders are perpetrated, for which no one is ultimately tried, than in Italy or in England; that is to say, a murderer runs more risk of being placed in the dock in this country than in France.  But the difference between the two countries is again to a great extent adjusted by the fact that once a man is placed in the dock in France he has far less chance of being acquitted than if he were tried according to English law.  On the whole, therefore, it may be assumed that the international statistics of trials, corrected when necessary by the international statistics of convictions, present a tolerably accurate idea of the extent to which the crime of murder prevails among the nationalities of Europe.  In any case these figures will go some way towards helping us to see whether climatic conditions have any influence upon the amount of crime.  This we shall now inquire into.

On looking at the isotherms for the year it will be observed that the average temperature of Italy and Spain is ten degrees higher than the average temperature of England.  On the other hand, the average temperature of Hungary is very much the same as the average temperature of this country; but Hungary is at the same time exposed to much greater extremes of climate than England.  In winter it is nearly ten degrees colder than England, while in summer it is as hot as Spain.  The advocates of the direct effect of climate upon crime contend that account must be taken not merely of the degree of temperature, but also of the variations of temperature to which a region is exposed.  According to this theory one of the principal reasons the crime of murder is, at least, fourfold higher in Hungary than in England, is to be found in the violent oscillations of temperature in Hungary as compared with England.  In Italy murders are, at least, ten times as numerous as in England; in Spain they are seven times as numerous; the chief cause of this condition of things is said to be the serious difference of temperature.  In the United States of America there are more crimes of blood in the South than in the North; the main explanation of this difference is said to be that the climate of the South is much hotter than the climate of the North.