Will-o-the-Wisp and Corpse-lights; Underground Folk

The will-o-the-wisp, if not unknown, is at least extremely rare. The name Lughaunaguinnell, or Loughaguinnell, of a pool in Doora refers, I was told, to a ‘candle’ floating over its surface. In the name Doora itself we find the ancient word for water, which occurs as the river Dour in Kerry in Ptolemy’s Atlas in the first century. Mr. and Mrs. Hall, in ‘Ireland: its Scenery, Character, etc.’ (1841), note that one of their guides told them of ‘corpse candles’ seen on the banks of the Shannon, and voices of the ‘good people’ heard with them. Crofton Croker, in ‘Florry Cantillon’s Funeral’, ^[47] alludes to the ‘Blue Man’s Lake at midnight,’ a lonely place in the bog at Shragh, near Kilrush, where ‘a spectral figure enveloped in a bluish flame’ haunted the melancholy waters. Some of the ‘corpse lights’ shining in graveyards, ‘forts,’ and deserted buildings I have myself seen. In one case, I traced the light to the stagnant water, full of rotten leaves, in the fosse of a ‘fort,’ which, when stirred by waving branches, gave out phosphorescent light. In another case a church gable was observed for many nights lit up with blue flame, after three victims of a railway accident had been laid in their family vault below it. The windows of Inchiquin Castle are seen across the lake, lit up by pale blue fire, which vanishes from the sight of anyone approaching the ruined building though still visible at a distance. A deserted cottage on a ridge not far from Tulla, as I have seen, used to be lit up with pale light, and was reputed haunted. Several graveyards have displayed ‘corpse lights,’ and particularly those at Killone Convent (a picturesque twelfth-century ruin on a wooded slope over a beautiful lake near Ennis), and, I hear, Killeemur and Kilmaleery on the Shannon and Fergus, and Clooney in Bunratty Barony.

Undergound Folk
To underground folk, other than fairies, I have only found few and uninteresting references, such as—‘an old woman looked out of the side of the fort, and the man ran away’; ‘he heard them talking inside the hill’; and ‘the little old man came out of the fort, and shut it behind him.’