Unsung scientist. Born into modest surroundings on the farm of Little Whitefield, near Wolfhill (Perth and Kinross), Croll was largely self-educated through a passion for reading. He became an apprentice millwright at Collace and then a joiner, but gave that up due to ill-health. Thereafter he was, successively, a tea merchant in Perth then in Elgin, manager of a temperance hotel in Blairgowrie and an insurance agent in Glasgow, Dundee and Edinburgh, before moving to Paisley and being appointed as a janitor in the museum at Anderson's Institution (Glasgow) in 1859.
Croll corresponded with Sir Charles Lyell (1797 - 1875), sending him his ideas of links between ice ages and variations in the earth's orbit. This gained Croll a clerical position in the Geological Survey of Scotland (1867-81), where he was encouraged by Archibald Geikie (1835 - 1924). Later, Charles Darwin also corresponded with Croll and benefited from his ideas.
Croll's many works included The Philosophy of Theism (1857), Climate and Time, in their Geological Relations (1875), Climate and Cosmology (1885) and The Philosophic Basis of Evolution (1890). His work which linked climate to orbital variations was well ahead of its time. Now called "Milankovitch Cycles", credit went to a Serbian scientist born four years after Croll's book was published and more than fifteen years after he began developing these ideas.
Croll was elected a Fellow of the Royal Society in 1876 and awarded an honorary degree by the University of St. Andrews in the same year.
He died in Perth.