In the localities where climate, soil, and physical conformation tended least to separate men as they increased, and where, accordingly, the first civilizations grew up, the internal resistances to progress would naturally develop in a more regular and thorough manner than where smaller communities, which in their separation had developed diversities, were afterward brought together into a closer association. It is this, it seems to me, which accounts for the general characteristics of the earlier civilizations as compared with the later civilizations of Europe. Such homogeneous communities, developing from the first without the jar of conflict between different customs, laws, religions, etc., would show a much greater uniformity. The concentrating and conservative forces would all, so to speak, pull together. Rival chieftains would not counterbalance each other, nor diversities of belief hold the growth of priestly influence in check. Political and religious power, wealth and knowledge, would thus tend to concentrate in the same centres. The same causes which tended to produce the hereditary king and hereditary priest would tend to produce the hereditary artisan and laborer, and to separate society into castes. The power which association sets free for progress would thus be wasted, and barriers to further progress be gradually raised. The surplus energies of the masses would be devoted to the construction of temples, palaces, and pyramids; to ministering to the pride and pampering the luxury of their rulers; and should any disposition to improvement arise among the classes of leisure it would at once be checked by the dread of innovation. Society developing in this way must at length stop in a conservatism which permits no further progress. How long such a state of complete petrifaction, when once reached, will continue, seems to depend upon external causes, for the iron bonds of the social environment which grows up repress disintegrating forces as well as improvement. Such a community can be most easily conquered, for the masses of the people are trained to a passive acquiescence in a life of hopeless labor. If the conquerors merely take the place of the ruling class, as the Hyksos did in Egypt and the Tartars in China, everything will go on as before. If they ravage and destroy, the glory of palace and temple remains but in ruins, population becomes sparse, and knowledge and art are lost.