We may add that the distances between what we may call megalithic zones is considerable. We meet, for instance, with dolmens in Circassia and in the Crimea, but there are no others nearer than the Baltic. There are none in the districts peopled by the Belgæ, from the Drenthe to the borders of Normandy, nor are there any in the valleys of the Rhine or of the Scheldt. There are but a few in Italy or in Greece, where Pelasgic buildings were early erected, and bore witness to a more advanced civilization. We meet with them again, however, in Palestine, but we must traverse many miles before we find other examples at Peshawur and in the valley of Cabul. It is difficult to overrate the importance of these facts, or to explain these gaps. Are they, however, so complete as has been supposed? The few travellers who have crossed Afghanistan and Daghestan have seen tumuli which may have served as points of union between the monuments of India and those of the Caucasus. The megalithic monuments of Palestine and of Arabia may yet be found to be linked with those of Algeria, by examples in the little known regions between the Nile and the Regency of Tripoli. If our ignorance forbids us to assert anything on this point, it equally forbids our denying anything with any confidence. We may also add one general remark: the countries where megalithic monuments are found, abound in granite, in sandstone, and in flint, whilst other districts have only very friable limestones; and, their monuments, if they were ever erected, would have been more easily destroyed, the very ruins disappearing and leaving no trace.