[Ms. cost books (4) for mines in Cornwall which also contain some draft and copy correspondence and some accounts of Richard Trevithick. The two volumes (/1-/2) chiefly containing copy correspondence are mostly of Trevithick, especially with J. U. Rastrick and with Hazledine, Rastrick & Co., although /1 is prefaced by 'Eastern Stray Park Costs' 1790-2, and /2 by Wheal Treasury costs 1795-7. /2 concludes with some entries re Trevithick in South America. The two volumes (/3-/4) chiefly contain accounts, with numerous individuals c.1812-13, and mines from 1765 onwards]