William Nicol (geologist)

William Nicol
Born	1768
Nationality	Scottish
Known for	invented theNicol prism,the first device for obtaining planepolarizedlight

Nicol's house, 12 Inverleith Terrace, Edinburgh

Memorial to William Nicol, Warriston Cemetery

William NicolFRSEFCS (1768? – 2 September 1851) was a Scottishgeologistandphysicistwho invented theNicol prism,the first device for obtainingplane-polarized light,in 1828.

Early life

Nicol was born inHumbie(East Lothian), the son of Walter Nicol and Marion Fowler.According to the parish register, he was born 18 April and baptised on 22 April 1770. Some sources give his date of birth as 1768;other ones (including his gravestone) give 1766. (Note that the gravestone date may be incorrect, as the engraving was done at least 50 years after his death.)

Lecturer

He started out as aide to his uncle,Henry Moyes,an itinerant lecturer inNatural Philosophywhose blindness necessitated assistance for his chemistry and optics demonstrations.Nicol, having himself become a popular lecturer on that subject at theUniversity of Edinburgh,settled inEdinburghto live a very retired life. Besides the prism that bears his name, he conducted extensive studies offluid inclusionsin crystals and the microscopic structure offossilwood.He did not publish any of his research findings until 1826.

Nicol prism

Main article:Nicol prism

Nicol made his prism by bisecting aparallelepipedofIceland spar(a naturally occurring, transparent crystalline form ofcalcium carbonate) along its shortest diagonal, then cementing the two halves together withCanada balsam.Light entering the prism isrefractedinto two rays, one of which emerges as plane-polarized light. Nicol prisms greatly facilitated the study of refraction andpolarization,and were later used to investigatemolecularstructures and optical activity oforganiccompounds.

Microscopic petrography

In 1815,Nicol developed a method of preparing extremelythin sectionsofcrystalsandrocksformicroscopicalstudy. 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 ofCanada balsamto 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 transparent to translucent layer adhering to the glass, and the requisite degree of transparency was obtained. His technique of makingthin sectionsmade 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 byHenry Withamin hisObservations of Fossil Vegetables(1831), to which Nicol supplied the first published account of the process.

When Nicol died, his instruments and preparations passed toAlexander 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 byDavid Brewsterand Nicol.

Death and legacy

He died at his home, 4 Inverleith Terrace inEdinburgh(now renumbered 12 Inverleith Terrace) on 2 September 1851,and was buried inWarriston Cemetery.His burial site is now marked by a plaque on the east wall, north of the sealed eastern gate.

Dorsum Nicolon theMoonis named after him.