As Regius Professor of Natural History at the University of Edinburgh for fifty years, developing his predecessor John Walker's concepts based on mineralogy into geological theories of Neptunism which held sway into the 1830s.
[3] By 1793, influenced by the Regius Professor of Natural History, John Walker (1731–1803), Jameson abandoned medicine and the idea of being a ship's surgeon, and focused instead on science, particularly geology and mineralogy.
It is worth noting that Walker was a presbyterian Minister who had actually combined the Regius Professorship with a period of service as Moderator of the General Assembly of the Church of Scotland in 1790.
During this time his geological field-work frequently took him to the Isle of Arran, the Hebrides, Orkney, the Shetland Islands and the Irish mainland.
As an undergraduate, Jameson had several noteworthy classmates at the University of Edinburgh including Robert Brown, Joseph Black, and Thomas Dick.
[4] In 1804, Jameson succeeded Dr Walker as the third Regius Professor of Natural History at the University of Edinburgh, a post which he held for fifty years.
Jameson's support for Neptunism, a theory that argued that all rocks had been deposited from a primaeval ocean, initially pitted him against James Hutton (1726–1797), a fellow Scot and eminent geologist also based in Edinburgh (but not in the university), who argued for the uniformitarian deistic concept of Plutonism, that features of the Earth's crust were endlessly recycled in natural processes powered by magmatic molten rocks.
"[7] – this was the first use of the word "evolved" in a modern sense,[8] and was the first significant statement to relate Lamarckism to the geological record of living organisms of the past.
[9] Attribution has been disputed, the concepts point to Jameson as the author, combining the directional geological history of Earth proposed by Neptunism with progressive transformism (transmutation of species) shown by fossils.
Over Jameson's fifty-year tenure, he built up a huge collection of mineralogical and geological specimens for the Museum of Edinburgh University, including fossils, birds and insects.