Prism, of Iceland spar

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This 'Nicol' prism cut from Iceland spar was made to demonstrate the spar's double refraction property. David Brewster was an Edinburgh polymath whose most important optical discoveries were concerned with the nature of polarised light.

A Nicol prism is made by splitting a crystal of Iceland spar along its shorter diagonal plane and cementing the parts together with Canada balsam. A beam of light is doubly refracted when it enters the crystal.

The doubly refracting qualities of Iceland spar first came to the attention of natural philosophers in the 17th century but it became useful as an experimental tool only after Edinburgh geologist William Nicol invented his prism in 1829.

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• Online ID: 000-100-102-843-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1967.181
• Date: 19th century
  
• Material: Iceland spar, digonal crystal calcite
  Crystal / Iceland spar
  
• Dimensions: 120 mm x 70 mm x 60 mm
  
• What: Crystal / Iceland spar
  
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• Description: Crystal of Iceland spar, a large cleavage rhomb of the digonal crystal calcite, 19th century
  
• References:
  • Morrison-Low, A.D. & Christie, J.R.R. (eds.), Martyr of Science: Sir David Brewster 1781-1868. Edinburgh: 1984, p 87 
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