He went to school at the Ayr Academy, and then was placed in the counting-house of Charles Macintosh in Glasgow.
Clark took a seat in the university court of St. Andrews, as assessor appointed by the rector, John Stuart Mill, who had known him for many years.
His soap test for hardness, patented in 1841,[2] was quickly taken by the government for waters proposed to be supplied to towns.
Although the process was favourably reported on to the government in 1851 by Graham, Miller, and Hoffmann, it was opposed by the metropolitan water companies, and was adopted in only a few places.
After he became unable to teach he studied English philology and grammar, and the gospels of the Greek Testament.