John Walker lived from 1730 to 1803. He was a churchman and a leading naturalist who became an important figure in the Scottish Enlightenment. The wider picture in Scotland at the time is set out in our Historical Timeline.
John Walker was born in Canongate, once a separate burgh immediately to the east of Edinburgh, which now exists primarily in the name of the lower half of the city's Royal Mile. In 1746 he became a student at the University of Edinburgh, emerging with a divinity degree in 1749. He was then ordained into the Church of Scotland and spent the fifty years until his death in 1803 as a parish minister, successively serving the parishes of Glencorse, Moffat and Colinton.
In parallel with his ministry, Walker pursued a wide range of other interests. During the 1750s he studied chemistry at Edinburgh University under William Cullen, and he joined Edinburgh's Philosophical Society. Such was his success as a chemist that he was soon appointed as the part time scientific advisor to the Judge Advocate Lord Kames.
During the 1760s, Walker became interested in geology and built up a considerable personal collection of specimens. In 1764 and 1771 he was sent on tours of the Highlands and the Hebrides during which he collected religious and ethnographic material for the Church of Scotland, and made scientifically oriented notes on the area's minerals, plants, animals, and climate. In 1783, Walker was a founding member of the Royal Society of Edinburgh.
In 1779 Walker was appointed Regius Professor of Natural History at Edinburgh University, a post he continued to hold until his death. The subjects he covered in his lectures were wide ranging, including meteorology, hydrology, geology, minerals, botany, agriculture, and zoology. Among his notable students were John Playfair and Sir James Hall. With hindsight, Walker can be seen to have become a leading light in the scientific strand of the Scottish Enlightenment.
Throughout all this, Walker continued to perform his duties as a parish minister: though how he managed to divide his time successfully in an age of relatively poor transport links is unclear. In 1790 he was appointed Moderator of the General Assembly of the Church of Scotland for the year. Walker began to lose his sight in 1797, and an increasing number of his lectures had to be given instead by his student and assistant Robert Jameson, who was subsequently appointed Regius Professor of Natural History after Walker's death in 1803.