The circle is but an elaboration of a monolith surrounded by stones. There is, however, every indication that it was introduced into this country after it had passed through all its stages of evolution and assumed its final form. Its builders made their way hither from the south, spreading more especially over Spain, Brittany and Denmark on the mainland, and on arriving upon our southern coasts, branching northward through England and Scotland, even to the Orkneys, on the one side, and by sea to Ireland and the Western Hebrides on the other. Thus the date of its advent must have been subsequent to the mastery of navigation. It has been assumed that because Stonehenge represents the finished design, it must be the latest of our English examples, and, therefore, the evolution of those rude, and often unhewn, monuments of which so many examples have weathered more than two thousand winters on the high-lands of the Peak. But the very opposite proposition probably represents the truth. In the whole of our isles there is no other example of a trilithic design, so the theory of local evolution must fail. On the other hand, we trace it without a fault from India, through Arabia, along the north coast of Africa, in Malta and Minorca, and finally on the coast of Brittany, on its way to this island. Again, the curious architectural joint of mortice and tenon, which is so interesting a feature of Stonehenge, is unknown here, but present in the trilithons of the Mediterranean shores. [Illustration: Arbor Low: General View of the Southern Half.] We may, therefore, infer that the builders of Stonehenge were of a race which originally came from the south, and that the monument was erected under the direction of men who had seen or had, at least, been thoroughly instructed in the architecture of the earlier trilithons. This was their work, but after them came the copyist and the invariable deterioration. A parallel case is that of the introduction of the art of coinage into this country about B.C. 200. It found its way to us over nearly the same route, and in its earliest stages was, therefore, an imitation of the Greek and Phœnician money then current; but before many years had passed many of the designs had degenerated into conventional figures, often of a distinctive character, yet evolved by the exaggeration of some minor detail upon the prototype. Another comparison may be made with the customs of burial about the period we are considering. At first the useful and valuable flint implements of the deceased were, with a praiseworthy unselfishness, interred or cremated with his remains; but later, this sometimes became a mere matter of ceremony, and it was thought sufficient to substitute flint chippings for these offerings.