Article Text

Download PDFPDF
Doubling up: two prisms, two names, two countries
  1. Richard Keeler,
  2. Arun D Singh,
  3. Harminder S Dua

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Cover image courtesy of Mr Richard Keeler, Curator, museum of the Royal College of Ophthalmologists, UK. Cover photo: Mark Thomas

Sir John Herschel, born in Slough, England in 1792, was a distinguished mathematician and astronomer. His father, German-born Friedrich Wilhelm Herschel (Sir Frederick William Herschel) discovered the planet Uranus. One of Sir John's many contributions to science was the concept that two prisms of equal power when rotated in opposite directions give gradually increasing power from zero to double the power of each individual prism. Based on this principle he developed an optical instrument with rotating …

View Full Text


  • Provenance and peer review Not commissioned; not externally peer reviewed.