William Nicol (geologist)
He was born in Humbie (East Lothian) in 18 Apr 1770 and his birth and baptism is recorded in the parish register; many sources give an incorrect date of birth. For example, the Royal Society of Edinburgh gives a date of birth of 1768, and his gravestone gave a date of birth of 1766.
He started out as aide to his uncle, Henry Moyes, an itinerent lecturer in Natural Philosophy whose blindness necessitated assistance for his chemistry and optics demonstrations. Nicol, having himself become a popular lecturer on that subject at the University of Edinburgh, settled in Edinburgh to live a very retired life. He conducted extensive studies of fluid inclusions in crystals and the microscopic structure of fossil wood. He did not publish any of his research findings until 1826.
Nicol made his prism by bisecting a parallelepiped of Iceland spar (a naturally occurring, transparent crystalline form of calcium carbonate) along its shortest diagonal, then cementing the two halves together with Canada balsam. Light entering the prism is refracted into two rays, one of which emerges as plane-polarized light. Nicol prisms greatly facilitated the study of refraction and polarization, and were later used to investigate molecular structures and optical activity of organic compounds.
In 1815, Nicol developed a method of preparing extremely thin sections of crystals and rocks for microscopical study. He hit upon the plan of cutting sections of fossil wood, so as to reveal its minutest vegetable structures under a microscope. He took a slice from the specimen to be studied, ground it perfectly flat, polished it, and cemented it by means of Canada balsam to a piece of plate-glass. The exposed surface of the slice was then ground down, until the piece of stone was reduced to a thin pellicle adhering to the glass, and the requisite degree of transparency was obtained. His technique made it possible to view mineral samples by transmitted rather than reflected light and therefore enabled the minerals' internal structures to be seen. Nicol prepared a large number of slices of fossil and recent woods. Many of these were described by Henry Witham in his Observations of Fossil Vegetables (1831), to which Nicol supplied the first published account of the process.
When Nicol died, his instruments and preparations passed to Alexander Bryson, who made many additions to the collections and made numerous thin slices of minerals and rocks for the purpose of exhibiting the cavities containing fluid, which had been described long before by David Brewster and Nicol.
Death and legacy
- Joseph Priestley to Joseph Banks, 6 Feb 1783, NHM, Dawson Turner MS 3, fol. 17
- p122 Albert Edward Musson, Eric Robinson Science and technology in the Industrial Revolution, Manchester University Press, 1969, ISBN 0-7190-0370-9
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Sir Archibald Geikie, The Founders of Geology (1897)