Born in Dalavich, Argyll and resident for most of his life in Paisley and Elderslie where he was in business as a surveyor, MacFarlane was a notable Gaelic activist and writer from the late 1880s. He played a prominent part in the early years of An Comunn Gaidhealach (particularly in the production of its magazine, An Deò-Gréine, later An Gaidheal) while, as a radical in politics, taking issue with what he regarded as the An Comunn leadership's over-deference to aristocratic patronage and influence. His correspondents include very many of the writers and scholars active in Gaelic life during this period: Henry Whyte (“Fionn”, 1852-1913), is a particularly regular correspondent. MacFarlane's contacts with Douglas Hyde and other members of the Gaelic League of Ireland, and with other pan-Celtic organisations, is also represented in the correspondence. His musical compositions, arrangements and re-arrangements are very well represented as is his work on Gaelic dictionaries. The papers include some manuscripts of friends, presumably submitted to him for comment, notably work of the Mull-born John MacCormick (died 1947), author of short stories and of the first substantial novel in Gaelic.