Before the end of his life, MacDonald dedicated himself to teaching Latin, history, and philosophy to many students in schools around Dunoon and Glasgow in Scotland.
[citation needed] MacDonald published books and historical monographs on the history of early and medieval Britain, and in particular Scotland and the Gaelic speaking peoples.
[6] The works of MacDonald represent an important turning point in Scottish history and provide some of the most comprehensive research on the life, culture, and languages of the Highlands and Islands of Scotland.
His work is buttressed by thorough use of original sources and first-hand accounts from elder highlanders who were unable to write in English.
[7] Towards the end of his life, MacDonald dedicated himself to teaching Latin, history, and philosophy to the next generation of students in Dunoon and Glasgow in Scotland.