Ymenyn Y Tylwyth Teg Or Fairy Butter
: FAIRY MEN CAPTURED.
: Welsh Folk-lore
I cannot do better than quote Pennant on this matter. His words are:--
Petroleum, rock oil, or what the Welsh call it, Ymenin tylwyth
teg, or Fairies' butter, has been found in the lime stone strata in
our mineral country. It is a greasy substance, of an agreeable
smell, and, I suppose, ascribed to the benign part of those imaginary
beings. It is esteemed serviceable in rheumatic cases, rubbed on the
parts affected. It retains a place in our dispensary.
Pennant's Whiteford, p. 131.