Footnotes

• John Cuthbert (1783-1854) was a respected optician who made a number of reflecting telescopes. In 1826 he began making a small number of reflecting microscopes in response to the demand to improve the resolution of the microscope image which suffered from chromatic aberration. Lister's publication in 1830 of the new design of refracting objective made the reflecting microscope redundant.
  
  There are believed to be only twelve known Cuthbert reflecting microscopes extant.
  
  M.B-L comments: "Because of the problem of “coma” (multiple images produced by the high curvature of microscope objective lenses), achromatic lenses invented by John Dolland (in 1765) did not work on microscopes at this date. In order to get round the problem of colour aberration (rainbow coloured fringes round the images due to the variable refraction of the different wavelengths of light passing through glass), Cuthbertson used Newton’s solution for telescopes, namely substituting a mirror for the objective lens. Making tiny perfect concave mirrors was doubtless extremely difficult and time consuming even for a craftsman as skilled as Cuthbertson undoubtedly was. The actual mirrors on this microscope are worth examining as they are exquisite little works of art in themselves. The time and complication of making this microscope meant that they were very expensive and only a small number were ever made."