Has the great shadeless desert nothing to do with the habits of the nomade tribes who pitch their tents upon it--the fertile plain no connection with flocks and pastoral life--the mountain fastnesses with the courage that has so often defended them--the sea with habits of adventure? Indeed, do not all our expectations of the stability of social institutions rest upon our belief in the stability of surrounding physical conditions? From the time of Bodin, who nearly three hundred years ago published his work 'De Republica,' these principles have been well recognized: that the laws of Nature cannot be subordinated to the will of Man, and that government must be adapted to climate. It was these things which led him to the conclusion that force is best resorted to for northern nations, reason for the middle, and superstition for the southern. [Sidenote: Effects of the seasons on animals and plants.] In the month of March the sun crosses the equator, dispensing his rays more abundantly over our northern hemisphere. Following in his train, a wave of verdure expands towards the pole. The luxuriance is in proportion to the local brilliancy. The animal world is also affected. Pressed forward, or solicited onward by the warmth, the birds of passage commence their annual migration, keeping pace with the developing vegetation beneath. As summer declines, this orderly advance of light and life is followed by an orderly retreat, and in its turn the southern hemisphere presents the same glorious phenomenon. Once every year the life of the earth pulsates; now there is an abounding vitality, now a desolation. But what is the cause of all this? It is only mechanical. The earth's axis of rotation is inclined to the plane of her orbit of revolution round the sun. Let that wonderful phenomenon and its explanation be a lesson to us; let it profoundly impress us with the importance of physical agents and physical laws. They intervene in the life and death of man personally and socially. External events become interwoven in our constitution; their periodicities create periodicities in us. Day and night are incorporated in our waking and sleeping; summer and winter compel us to exhibit cycles in our life. [Sidenote: Individual existence depends on physical conditions.]