1"Pre-Christian Ireland." Irish Identity. Web. 27 May 2011. <http://www.irishidentity.com/stories/prechristian.htm>.
From this source: "The historian Geoffrey Keating later wrote ... 'I cannot conceive how the Irish antiquaries could have obtained the accounts of those who arrived in Ireland before the Flood, unless they were communicated by those aerial demons, or familiar sprites, who waited on them in times of paganism, or that they found them engraved on stones after the Deluge had subsided.'"
" Geraldus Cambrensis agrees with the latter more acceptable explanation ... i.e. the theory of the information being derived from hieroglyphics and engravings on stone or on the inner walls of caves."