'Sold to Stewart'

Another annotation to the 1804 Map of Harris. In the sea, adjacent to Ensay, we have the words 'Sold to Stewart'.
According to RCAHMS, the island of Ensay was occupied by Archibald Stewart of Luskentyre, Lord Dunmore's Factor,  from 1856. This gives us an earliest possible date for the annotation but I am confused by the attribution of Factor?

The Factor at this time was John Robson Macdonald. Was it he who wrote on the map or, perhaps, the 7th Earl of Dunmore himself? Although he was only 15 in 1856, I suspect the writing to be slightly later, and perhaps of the time when the Earl took control of Harris himself and began his building projects in North Harris. One piece of evidence supports this. Near Meavaig, in the North, the same hand wrote 'Proposed Site For Lodge' and, in the sea at the mouth of the loch, a single word - 'oysters'. Somehow that strikes me more the work of a man in his early twenties rather than his middle-aged Factor.

A flight of fancy, but I believe it highly likely that on Bald's 1804 Map of Harris we have samples of the handwriting of Charles Adolphus Murray, the 7th Earl of Dunmore!

Update: As explained in my Update to http://direcleit.blogspot.com/2010/05/obe-harris-thursday-may-311883.html , we have corroboration from evidence to the Napier Commission that the sale of the outlying islands to 'Stewart' took place at the behest of the 7th Earl and not too many years prior to 1883. The provenance of the map is uncertain, but I think the annotations, taken with the supporting evidence I have been able to garner, are sufficient to establish that it was in active use as the Estate map during the second-half of the 19thC although whether kept in Rodel by the Factor or on the mainland by his master (and written on by one or both men) will remain uncertain for the present.