The tinklarian Doctor's twenty first epistle, which contains three new lights, concerning Captain Porteous, two of these great Lights was written in his Life-Time, the other after his Death. Written in the 66 Year of his Age. I dedicate this wonderful epistle to their Majesty's, [sic] both to the King and to the Queen, I know their Majesty's will understand it, because their Majesty's gave me two Guineas for my Light, before their Majesty's was set on the Throne: Long may their Majesty's live; and well may their Majesty's prosper, is the prayers of William Mitchell.