Monica, "Mupellro" is indeed meant to be Musselburgh.
I've now traced Jessie Gordon back to her parents Samuel Gordon and Margaret Nicholson of Musselburgh, and Samuel Gordon back to his parents Alexander Gordon and Isabel or Isabella Clark of Kells, Kirkcudbright. Unfortunately, when I searched for their children I found only Alexander (baptised 1803), Isabella (1805), Samuel (1807) and William (1811). I had high hopes for a John around 1813 (and a James of similar vintage who was named as an executor in John Gordon's will in 1848 but either didn't accept the appointment or didn't survive to do so on John Gordon's death in 1850).
I can't help wishing that John had been granted a more exotic name so as to narrow down the possibilities!
Anne