19th of Arrochar, and 20th chief of the Macfarlane clan. Son of John Macfarlane of Ardess (d. 1705) and Helen Arbuthnot (1675-1741). Half-brother (on his mother's side) of John Spottiswoode. Married (1760) to Elizabeth Erskine.
Macfarlane was arguably the most respected antiquarian and genealogist in 18th century Scotland, leading the University of Glasgow to confer on him an honorary degree of Doctor of Laws on January 25, 1756.
Boswell visited him in London on November 21, 1762, discussing the feud between the Scots and the English. He also saw him on various occasions in the company of his wife and her family, who arrived in London around December 1, 1762, and stayed until March 14, 1763.
Boswell may have had some disagreements with Macfarlane - on 27/12-1762 he mentioned that he had tea with Lady Betty and that he no longer intended to refer to the Macfarlane name. The journal doesn't tell us why. On January 18, 1763, however, Macfarlane tells James that "you are welcome on your own account. But suppose that was not the case, I owe your father as many dinners". They seem to have gotten on well for the remainder of his London stay.
In his journal entry of September 25, 1764, while staying at the court of Anhalt-Dessau, Boswell wrote, in connection with a hunt:
"A large stag was single out, and away we went after him. It was the first time that I saw this sport, and a most noble one it is. Macfarlane would say, "Then it might be a marquis, for Most Noble is his title."
To this statement, the editors of Boswell on the Grand Tour (vol 1) attached a footnote reading that
"Boswell's elderly friend Walter Macfarlane of Macfarlane, an antiquary, might be expected to be punctilious in such matters. The proper style of a marquis is "Most Honourable"."
Macfarlane's massive collection of geographical, topographical and historical material was published as "Macfarlane's Geographical Collections relating to Scotland" (3 vols) in 1906-8 by the Scottish Historical Society, edited by Sir Arthur Mitchell and James Toscach Clark. It is available fairly inexpensively via AbeBooks, but beware of on-demand prints.