_Burn at Croydon_ (Vol. vii., p. 283.).--This seems to be of the same
nature as the "nailburns" mentioned by Halliwell (_Arch. Dict._). In
Lambarde's _Perambulation of Kent_, p. 221., 2nd edit., mention is made
of a stream running under ground. But it seems very difficult to account
for these phenomena, and any geologist who would give a satisfactory
explanation of these _burns_, _nailburns_, subterraneous streams, and
those which in Lincolnshire are termed "blow wells," would confer a
favour on several of your readers.