Then how came Rome to be the foundress and the great source of law? This, as we said before, calls for a separate explanation. An explanation we do not pretend to give, but merely a hint which may deserve notice in looking for the explanation. In primitive society, in place of law, in the proper sense of the term, we find only tribal custom, formed mainly by the special exigencies of tribal self- preservation, and confined to the particular tribe. When Saxon and Dane settle down in England side by side under the treaty made between Alfred and Guthurm, each race retains the tribal custom which serves it as a criminal law. A special effort seems to be required in order to rise above this custom to that conception of general right or expediency which is the germ of law as a science. The Greek, sceptical and speculative as he was, appears never to have quite got rid of the notion that there was something sacred in ancestral custom, and that to alter it by legislation was a sort of impiety. We in England still conceive that there is something in the breast of the judge, and the belief is a lingering shadow of the tribal custom, the source of the common law. Now what conditions would be most favourable to this critical effort, so fraught with momentous consequences to humanity? Apparently a union of elements belonging to different tribes such as would compel them, for the preservation of peace and the regulation of daily intercourse, to adopt some common measure of right. It must be a union, not a conquest of one tribe by another, otherwise the conquering tribe would of course keep its own customs, as the Spartans did among the conquered people of Laconia. Now it appears likely that these conditions were exactly fulfilled by the primaeval settlements on the hills of Rome. The hills are either escarped by nature or capable of easy escarpment, and seem originally to have been little separate fortresses, by the union of which the city was ultimately formed. That there were tribal differences among the inhabitants of the different hills is a belief to which all traditions and all the evidence of institutions point, whether we suppose the difference to have been great or not and whatever special theory we may form as to the origin of the Roman people. If the germ of law, as distinguished from custom, was brought into existence in this manner, it would be fostered and expanded by the legislative exigencies of the political and social concordat between the two orders, and also by those arising out of the adjustment of relations with other races in the course of conquest and colonization.