Definition of "wheal"

A Perſon of Honour, of a full Body abounding with ſharp Humours, was ſeized with an Herpes on his right Leg. […] [I]t inflamed and ſwelled very much, many Wheals aroſe, and fretted one into another, with great Excoriation.

1676, Richard Wiseman, “[A Treatise of Tumors.] Of an Herpes”, in Severall Chirurgical Treatises, London: Printed by E. Flesher and J[ohn] Macock, for R[ichard] Royston bookseller to His Most Sacred Majesty, and B[enjamin] Took at the Ship in St. Paul's Church-yard, page 80

The four last-mentioned mines, Wheal Crowndale, Wheal Crebor, East Liscombe, and Wheal Tamar, are on the same lode, which ranges as usual from east to west, and are included in a space of about four miles in length.

1829, Thomas Moore, The History of Devonshire, page 528

Surrounding the village are the remains ot many mine workings including the picturesque gtoup of clifftop buildings thar were once part of one of the county's best known mines - Wheal Coares.

2003, Peter Long, The Hidden Places of Cornwall, page 85

If you look at the map there are ‘wheals’ all over the place. There's Wheal Rose, Wheal Plenty and Wheal Busy. Back on the tramroad the industrial communities come thick and fast as you head southeast to Wheal Rose.

2010, Julia Bradbury, Julia Bradbury's Railway Walks, page 27