Thomas Martin Lindsay, Dictionary of National Biography… (1912)
“ In 1856 the Free church erected a third theological college, at Glasgow, and Douglas was appointed tutor of the Hebrew classes. The year after (26 May 1857) he became professor, and held this position until his retirement on 23 May 1892. On the death of Dr. Patrick Fairbairn, Douglas succeeded him as principal (22 May 1875) , and held office till 26 May 1902. His whole public life was spent in Glasgow in close connection with its university and with its educational and social activities. ”
