It is quite obvious that the story as we have it is a conflation of two versions of the anecdote. In the one version the wine was brought by Frankish merchants and acquired by purchase; in the other it was provided by miracle. The composite story appears in LA and VG; LB knows the miraculous version only.
That Frankish merchants should have sailed up the Shannon and delivered a cargo of wine at a settlement in the heart of Ireland in the middle of the sixth century, is no mere extravagance. The subject of ancient Irish trade has been very fully investigated by the late Prof. Zimmer, and he has brought a large number of facts together which show that such an episode is a quite credible fragment of history.
The second version, though LB calls it miraculum insolitum, is one of the commonplaces of hagiography. Water was turned to wine by a host of saints, such as Colum Cille (LL, 839), Fursa (CS, 111), Findian (CS, 205), Lugaid (CS, 283), Aed (CS, 339), and others needless to specify. Fintan (CS, 404), and Munnu (CS, 503), blessed a cup in such wise that one of their followers, while appearing, in self-abnegation, to drink nothing but water for thirty years, was in reality enjoying the best wine! Saint Brynach drew wine from a brook and fishes from its stones (Cambro-British Saints, pp. 12, 298), Brigit (LL, 1241) and Colman Elo (CS, 441) turned water into ale; the former (LL, 1368) as well as Lugaid (CS, 269, 280) and Fintan (CS, 404) turned water into milk.
I have not found any exact parallel to the incident of the scented thumb.
There is a cognate tale in the Life of Colman, in which monks, thirsty with labour, expressed a doubt as to the reality of the heavenly reward, whereupon their eyes were opened to see a vision of the joys of the after-life (VSH, i, 265).
The Tendenz of the biographies of Ciaran is clearly marked in the hint at a parallel between the last supper of Ciaran and the Last Passover of Our Lord.
On the consecrated Paschal fire, see Frazer, Balder the Beautiful, vol. i, p. 120 ff.
Parallels.—Coemgen carried fire in his bosom (CS, 837, VSH, i, 236). Cadoc also carried fire in his cloak without injury (Cambro-British Saints, pp. 30, 319). Elsewhere we hear of flames which do not consume, as in the burning bush of Moses, and probably in imitation of it (Exod. iii, 2). Thus the magic fire that delivered Samthann from a forced marriage appeared to ignite a whole town, which, however, suffered no injury (VSH, ii, 253). The fall of fire from heaven in answer to prayer is most likely imitated from 1 Kings xviii, 38.
The verse extracts at the end of LB (which see) contain a form of this story incompatible with the prose narratives.
The boy slain but not torn by wolves is, of course, imitated from the Prophet whose story is told in 1 Kings xiii, which is directly quoted in LA.