Having been licensed as a preacher, in 1843 he was ordained as minister of Rhynie, Aberdeenshire, and in the following year he removed to Girvan, Ayrshire, to the pastorate of a small free-church congregation.
His attachment to the free church was loosened when he found that its members intended to retain in the entirety the rigid definitions contained in the Westminster Confession of Faith.
Advancing years compelled him to retire from the ministry in October 1890, and he then began to make selections from his published works to form a volume.
His skill as a dialectician was displayed in a series of lectures on Ernest Renan's Life of Jesus, delivered in Glasgow City Hall before large audiences in 1863, and afterwards published.
He also claimed to have verified another work widely accepted to be a forgery, Roger O'Connor's Chronicles of Eri, which he said was "forgotten or treated with contempt as an imposture, but now capable of verification in all substantial respects".
[1] He also contributed a remarkable series of letters to a Glasgow journal on Ptolemy’s map of Egypt, showing that the discoveries of Speke and Grant had been foreshadowed by the old geographer.