an epithet expressing want of colour. The word is Greek, being compounded of a privative, and χρώμα, colour. This term was first introduced into astronomy by De la Lande.

ACHROMATIC Telescopes, are telescopes contrived to remedy the aberrations in colours. They were invent... Achting ed by Mr John Dollond, optician, and have been since improved by his son and others. See ABBERRATION.

—A more particular account of the invention and construction of these instruments will be found under OPTICS.