Description: A compound monocular microscope.

Caption: Made by R & J Beck at London, in about 1905, this instrument is highly unusual because an analyzer is mounted on an arm which swings it into the optical train above the ocular (eyepiece). It is also directly linked to a sub stage analyzer. Normally the analyzer is incorporated into the body tube of the instrument so this instrument may be a private commission by Beck.

Introduction: A petrological microscope is used to analyze rocks and minerals by the characteristic way that light is polarized or rotated when it passes through transparent thin sections of the minerals. By rotating the analyzer, until the extinction angle is observed, the component of rotation of the light by the specimen can be measured. the extinction angle is the point at which the darkest background around the specimen can be observed.

Background: This microscope is based on the work of William Nicol (1768-1851), Edinburgh born Professor of Natural Philosophy at the University of Edinburgh who invented the Nicol prism or crossed Nicol analyzer in1838. Nicol also invented the process for making thin sections of rocks and minerals in 1815.

Historical Context: Design - When: 1838 - Where: Edinburgh, Scotland - Who: Nicol, William (1768-1851) Born in Edinburgh, became professor of Natural Philosophy at Ediburgh University

Historical Context: Donation by the Department of Geology and Applied Geology to the Hunterian Museum - When: 1997

Historical Context: Donation by the Department of Geology and Applied Geology to the Hunterian Museum, University of Glasgow - Where: Glasgow, Scotland

Historical Context: Donation to the Hunterian Museum - Who: Department of Geology and Applied Geology, University of Glasgow

Historical Context: Manufacture - When: circa 1905 - Where: 68 Cornhill, London, England - Who: R. & J. Beck