Wherever it has been possible to test it with sufficient accuracy, we find that Perry’s contention is substantially true, and that there is a definite relation between many areas rich in megalithic structures and deposits of metal which are known to have been worked in early days; the megalithic areas of the Baltic coincide fairly well with the coasts producing amber. Nevertheless there are many spots, rich in metals, and which are known or suspected to have been worked in early days, where megaliths, have not hitherto been noted, and on the other hand, dolmens and other such structures occur, sometimes with great frequency, in areas devoid of metals or other precious commodities. The problem is not quite so simple as it would appear from Perry’s account. Still, looking at the matter broadly in the light of information available at present, it does seem that, in western Europe at any rate, the megalithic monuments cluster thickest in or _around_ those regions which produced gold, copper, tin and amber, and which were readily accessible to maritime traffic, and that they coincide very closely with the lines of trade which I described in the last chapter. The exceptions, too, are not destructive to the hypothesis. In the British Isles we find that the megaliths in the main coincide with the metalliferous areas, though in some cases more closely with lead ores than with the metals previously mentioned. As lead does not seem to have been used in north-west Europe before 1000 /B.C./, these monuments must, if any connection be implied, date from a much later period than that which we are discussing. But a large number of megalithic structures are found in the region surrounding Salisbury Plain and in certain parts of the Cotswolds. These are some of those open chalk and limestone areas already mentioned, which were the early centres of population in this country. As we have seen, certain trade routes to Ireland seem to traverse these regions, and here the merchants would have obtained their supplies of food for the rest of their journey; it would not surprise us, therefore, if they introduced their cult here, and that these populous areas formed fresh centres of dispersion.