Here we have a medley of heterogeneous and antagonistic elements. Leisure is essential to culture; before leisure there must be an accumulation of wealth; the accumulation of wealth is dependent upon the food-supply; a surplus of food can only be easily obtained in warm climates. But labor is also essential to development, and excessive heat is opposed to labor. Labor, moreover, in order to produce leisure must be remunerative, and excessive cold is opposed to accumulation. It appears, therefore, that an excess of labor and an excess of leisure are alike detrimental to improvement. Again, heat and moisture are essential to an abundant supply of oxidized food. But heat and moisture, especially in tropical climates, act as a stimulant upon other rank productions, engendering dense forests, tangled brush-wood, and poisonous shrubs, and filling miasmatic marshes with noxious reptiles. These enemies to human progress the weaponless savage is unable to overcome. It is, therefore, neither in hot and humid countries, nor in excessively cold climates, that we are to look for a primitive civilization; for in the latter nature lies dormant, while in the former the redundancy of nature becomes unmanageable. It is true that in the tropics of America and Asia are found the seats of many ancient civilizations, but if we examine them one after the other, we shall see, in nearly every instance, some opposite or counteracting agency. Thus, the Aztecs, though choosing a low latitude in proximity to both oceans, occupied an elevated table-land, in a cool, dry atmosphere, seven or eight thousand feet above the level of the sea. The river Nile, by its periodic inundations, forced the ancient Egyptians to lay by a store of food, which is the very first step toward wealth. The rivers of India are, some of them, subject to like overflowings, while the more elevated parts are dry and fertile. Egypt was the cradle of European development. Long before the advent of Christianity, the fertile banks of the Nile, for their pyramidal tombs, their colossi, their obelisks and catacombs and sphinxes and temples, were regarded by surrounding barbarians as a land of miracles and marvels. Thence Greece derived her earliest arts and maxims. The climate of Egypt was unchangeable, and the inundations of the Nile offered a less uncertain water-supply than the rains of many other districts, and thus agriculture, while offering to the laborer the greater part of the year for leisure, was almost certain to be remunerative. Common instincts and common efforts, uniformity of climate and identity of interests produced a homogeneous people, and forty centuries of such changeless coming and going could not fail to result in improvement. [Sidenote: MR BUCKLE'S THEORY.]