"The title Marquis (sometimes appearing as Marquess) of Huntly was the secondary title of the Dukes of Gordon and was normally given to an eldest son, and although the Gordons were a Scottish clan Huntly itself is in England. The particular Marquis of Huntly referred to by Marshall was George, heir to the Dukedom of his father Alexander who was Marshall's employer and patron (for whom he was Steward of the Household). George ascended to the title in 1827 and remained until 1836, and when he died childless the Dukedom ended, while the Marquessate and Earldom of Huntly "devolved" upon a relative, then the 5th Earl of Aboyne (Charles Gore). Marshall worked for him for 30 years as a land steward, and in his spare time became conversant with mathematics, astronomy, clocks, mechanics and optics, as well as composing 300 tunes." (From The Fiddler's Companion, linked to above)

~Masato