[2] Before being apprenticed to his father, he was educated at the new Belfast Academical Institution, a school founded on progressive principles by the former United Irishman William Drennan, and other veterans of the radical politics of the 1790s.
[3][4] His first Irish language influence may have been his uncle, Robert MacAdam, who collected Gaelic songs and was a member of the Belfast Harp Society.
[6][7] MacAdam, who in time was said to be fluent in a dozen languages, perfected his command of Irish in course of his extensive travels across Ireland on behalf of the family business.
[8] With his older brother, James MacAdam, in 1846 he established the Soho Foundry in Townsend Street[9][10] At its height, before the death in 1861 of his brother (a naturalist and geologist who in the interim had become the first librarian of Queen's College, Belfast), the firm had a workforce of 250 and an international reputation for the production of turbine engines (horizontal water wheels developed in France by Benoît Fourneyron).
[9][11] MacAdam followed Samuel Neilson into Cuideacht Gaoidhilge Uladh (the Ulster Gaelic Society) when it was formed in 1828[11] under the chairmanship of Dr James MacDonnell and with the patronage of the Arthur Hill, Marquess of Downshire.
[12] MacAdam, who became the society's joint secretary, protested that efforts to "beguile the poor Catholics from their faith" had done "more harm to the language than foreign persecution for 300 years".
He was to discover, for example, that Charlement Street (now buried under the Castle Court shopping centre) was inhabited exclusively by Irish-speaking basket-makers from Omeath.
He likened the rapidity of change to one of the dissolving views of a magic lantern show, with steam and education transforming areas that "conquest and colonisation failed to effect in centuries".
An English–Irish dictionary, compiled with Mac Domhnaill, and which ran to more than 1,000 manuscript pages,[24] was never published (and lay undisturbed in the Queen's University Library until 1996).
[2] Although his friends did eventually create an annuity that allowed him to live in reasonable comfort, MacAdam's last years had been dogged by ill health and poverty.
Its editor, after an hiatus of thirty years, was Francis Joseph Bigger, a key figure in a new "northern revival" of the Irish language.