A common belief was that a long black horsehair thrown into a running stream instantly becomes a live eel or water snake. William Harrison, The Description of England (1587: 321) provides an early reference, although he reserved judgement on the truth of the matter, and in the early 19th century the author of the Denham Tracts (1895: ii. 29) admits to trying it himself as a boy in the north of England. Correspondence in N&Q (7s:2–4 (1886–7) under the heading ‘Animated Horsehairs’ indicates that this had been a very widely held notion in England, Scotland, and elsewhere, at all levels of society well into the late 19th century.
A different correspondent in N&Q reported a belief in eels as a cure for deafness. A woman at Lochleven, who was putting live eels into a bag, told him they were being sent to England to cure a lady of her deafness, and that this was a regular occurrence. Asked if she herself believed in the cure, she answered, ‘Od, I dinna ken, sir, but thae English doctors shudken’. (N&Q 5s:9 (1878), 65). A more generally reported medical use of eels was (and perhaps still is) to wear their skins as a garter as a preventative for cramp, or a cure for rheumatism. Enid Porter (1969: 47, 67, 72, 86–7) gives a full description of how to prepare the skin, plus other eel lore, and Opie and Tatem (1989: 132) give references starting in 1684. A further belief, not confined to Britain, asserts that eels like fish, are killed by thunder (N&Q 10s:2 (1904), 331–2).