It is evident also not only from Cæsar's statement, but also from several passages in our earliest extant writings, that one of the principal functions of the Druids was to act as haurispices, that is, to foretell the future, to unveil the hidden, to pronounce incantations, and ascertain by omens lucky and unlucky days. Hence we always find some of them living with the king in his royal rath; they are not only his priests, but still more his guides and counsellors on all occasions of danger or emergency. King Laeghaire had at Tara Druids and enchanters, who used to foretell the future by their druidism and heathenism;[10] and they announced the coming of the _tailcend_, or shaven-crown, that is St. Patrick, long before his arrival. They were powerful in charms and spells. They could bring snow on the plain, but could not, like Patrick, take it away; they could cover the land with sudden darkness, but could not, like him, dispel it. They were powerful for evil, but not for good; they could with the charm called the 'Fluttering Wisp,' strike their unhappy victim with lunacy, or afflict him by the elements; they would even promise to make the earth swallow him up, as they said it would swallow St. Patrick when he was preaching on the banks of the Moy in Tyrawley. Their incantations, too, were in some instances not only wicked, but filthy and unclean,[11] and as such were of course strictly prohibited by St. Patrick. The Druids of Gaul, although unwilling to commit their doctrines to writing, were acquainted with the use of the Greek letters. The British Druids of Anglesey were even more learned; and we must infer that the Irish Druids possessed a similar culture. They had 'books,'[12] when St. Patrick met them at Tara; and two of them were entrusted with the education of the king's daughters at Cruachan. They were also skilled in medicine, and possessed a knowledge of healing herbs; they discoursed to their disciples on the nature of things,[13] and had some knowledge of astronomy. Thus vested with mysterious and supernatural powers, and possessed of an esoteric learning, that was exclusively their own, the Druids were held in great reverence and fear. "Tara was the chief seat of the idolatry and druidism of Erin,"[14] but we also find them at Cruachan in Connaught, and at Killala beyond the Moy[15]--both royal seats of the kings of that province. They accompanied the kings in their journeys and were present sometimes on the field of battle.[16] They were generally dressed in white, but wore an inner tunic to which reference is sometimes made. It is probable that one or more of them abode in the Raths of all the great nobles, who claimed to be _righs_, or kinglets, in their own territories. They were sworn enemies of Christianity, and frequently attempted to take St. Patrick's life by violence or poison. In the remote districts of the country some of them remained for several centuries after