As has been indicated, jet, pearls, gold, and tin appear to have been searched for and found before bronze working became a British industry. That the early prospectors had experience in locating and working metals before they reached this country there can be little doubt. There was a psychological motive for their adventurous voyages to unknown lands. The distribution of the megalithic monuments and graves indicates that metals were found and worked in south-western England, in Wales, in Derbyshire, and Cumberland, that jet was worked at Whitby, and that metals were located in Ireland and Scotland. Gold must have been widely distributed during the period of the great thaw. It is unlikely that traces of alluvial gold, which had been located and well worked in ancient times, should remain until the present time. In Scotland no traces of gold can now be found in a number of districts where, according to the records, it was worked as late as the fifteenth and sixteenth centuries. Some of the surviving Scottish megalithic monuments may mark the sites of ancient goldfields that were abandoned in early times when the supplies of precious metal became exhausted. The great circles of Callernish in Lewis and Stennis in Orkney are records of activity in semi-barren areas. Large communities could not have been attracted to these outlying islands to live on the produce of land or sea. Traces of metals, &c., indicate that, in both areas in ancient times, the builders of megalithic monuments settled in remote areas in Britain for the same reason as they settled on parts of the Continent. A gold rod has been discovered in association with the "Druid Temple" at Leys, near Inverness. The Inverness group of circles may well have been those of gold-seekers. In Aberdeenshire a group of megalithic monuments appears to have been erected by searchers for pearls. Gold was found in this county in the time of the Stuart kings.
The close association of megalithic monuments with ancient mine workings makes it impossible to resist the conclusion that the worship of trees and wells was closely connected with the religion of which the megalithic monuments are records. Siret shows that the symbolic markings on typical stone monuments are identical with those of the tree cult. Folk-lore and philological data tend to support this view. From the root _nem_ are derived the Celtic names of the pearl, heaven, the grove, and the shrine within the grove (see Chap. XIII). The Celts appear to have embraced the Druidic system of the earlier Iberians in Western Europe, whose culture had been derived from that of the Oriental colonists.