A cult of stones was probably connected with the belief in the magical power of certain stones, like the _Lia Fail_, which shrieked aloud when Conn knocked against it. His Druids explained that the number of the shrieks equalled the number of his descendants who should be kings of Erin.[1143] This is an ætiological myth accounting for the use of this fetich-stone at coronations. Other stones, probably the object of a cult or possessing magical virtues, were used at the installation of chiefs, who stood on them and vowed to follow in the steps of their predecessors, a pair of feet being carved on the stone to represent those of the first chief.[1144] Other stones had more musical virtues--the "conspicuous stone" of Elysium from which arose a hundred strains, and the melodious stone of Loch Láig. Such beliefs existed into Christian times. S. Columba's stone altar floated on the waves, and on it a leper had crossed in the wake of the saint's coracle to Erin. But the same stone was that on which, long before, the hero Fionn had slipped.[1145] Connected with the cult of stones are magical observances at fixed rocks or boulders, regarded probably as the abode of a spirit. These observances are in origin pre-Celtic, but were practised by the Celts. Girls slide down a stone to obtain a lover, pregnant women to obtain an easy delivery, or contact with such stones causes barren women to have children or gives vitality to the feeble. A small offering is usually left on the stone.[1146] Similar rites are practised at megalithic monuments, and here again the custom is obviously pre-Celtic in origin. In this case the spirits of the dead must have been expected to assist the purposes of the rites, or even to incarnate themselves in the children born as a result of barren women resorting to these stones.[1147] Sometimes when the purpose of the stones has been forgotten and some other legendary origin attributed to them, the custom adapts itself to the legend. In Ireland many dolmens are known, not as places of sepulture, but as "Diarmaid and Grainne's beds"--the places where these eloping lovers slept. Hence they have powers of fruitfulness and are visited by women who desire children. The rite is thus one of sympathetic magic.