Keir, Basalt, and Cooling Glass, 1776
Keir, James (1735-1820). "On the Crystallizations Observed on Glass." Philosophical Transactions of the Royal Society of London, 1776, 66:530-542.
James Keir was not a geologist but a well-known chemist, who moved in an intellectual circle known as the Lunar Society that included James Watt and Matthew Boulton, of steam-engine fame, and Josiah Wedgwood, the maker of porcelain. In experiments with molten glass, Keir discovered that if glass were cooled very slowly, it did not assume a glassy structure, but instead became crystalline, very much like fine-grained basalt. In this paper of 1776, he suggested that perhaps he had discovered evidence that basalt was an igneous rock, and then made a remarkable intellectual leap, by suggesting that the basalt of the Giant’s Causeway was the product of a volcano.
Smith 1969, “Porcelain and Plutonism;” Stokes 1971, “Volcanic Studies by Members of the Royal Society of London, 1665-1780,” p. 63; Newcomb 1990, “Contributions of British Experimentalists to the Discipline of Geology, 1780-1820;” Scott, E.L., “Keir, James,” in DSB 7:277-278.