In addition to the permanent factors of soil and race, by means of which a nation is rendered capable of pursuing a successful course of development through a series of fortunate revolutions, there are other and variable influences which give rise to a continuous rebellious unrest. Pre-eminent among these influences is a climate characterized by periods of rapidly rising temperature, whereas a tropical climate induces absolute indolence in the inhabitants, so that in tropical countries history has nothing to record regarding class-struggles, conspiracies, and serious insurrections. The hot season in the southern regions of the temperate climes is a cardinal factor in the production of political disturbances. Lombroso has proved this by the utilization of material whose official origin appears to him to render it entirely trustworthy—namely, the data recorded in the Calendar of Gotha for the years 1791 to 1880. In this period we find an account of 836 revolts, rebellions, insurrections, etc., of which 495 took place in Europe. The maximum of the European disturbances took place in the month of July, whilst of the South American revolts, the maximum occurred in the corresponding month of the southern hemisphere—viz., January. The more recent records, relating to outbreaks in Argentina and Chile, confirm this conclusion. The smallest number of revolts occurred—in Europe, in November and December, and in South America, in May and June. If we examine the records of the individual European nations, we find that among all the nations of Southern Europe the summer is the principal time of disturbance. In the case of five nationalities (the Norwegians, Swedes, Danes, Poles, and Irish) the spring predominates. In one case only was there a maximum of revolts in winter; this was Switzerland, in which ten out of twenty-four recorded outbreaks occurred during the winter season. Another tabulation of the figures displays the predominance of the nationalities of Southern Europe in the statistics of insurrection. In Greece there were 95 revolts per 10,000,000 inhabitants, this being the maximum; in Russia, down to the year 1900, there were 0·8 per 10,000,000 inhabitants, this being the minimum. Dividing Europe into three zones, we find that in Northern Europe there were 12 revolts, in Central Europe 25, and in Southern Europe 56, per 10,000,000 inhabitants.