The difficulty surrounding the correct interpretation of certain passages in Adomnán's Vita Columbae is due to his misunderstanding of his main written source for these passages, Cumméne Ailbe. In particular, (1) the earthquake whose location is given as Italy at VC 1.28 is that which occurred at Constantinople on 14 December 557, and this mistake is due to the confusion of the suburb of Constantinople entitled Rhegium with the Italian town of the same name; (2) Guaire mac Aidáin was cleaning the wooden hull of his boat when he had the accident described at VC 1.47, so that the vexed term cristilia refers to the encrustation on the hull; (3) the 'sea-monsters' whose attack upon Cormac Ua Liatháin's craft is described at VC 2.42 are identifiable as dolphins; (4) the book borne by the angel whose alleged appearance to Columba is described at VC 3.5 had originally been described as 'the book of the succession of the kings of Dál Riata', not 'the glass book of the ordination of kings', so that Columba had merely blessed Aidán mac Gabráin in the knowledge that he would be king one day and had not actually ordained him such.