ANCIENTS AND OPTICS.

Ashburton Guardian, Volume 59, Issue 133, 18 March 1939, Page 8

ANCIENTS AND OPTICS.

THEIR LIMITED KNOWLEDGE. The reminder to the British Association that lenses were discovered as recently as the thirteenth century explains why the science of optics made so little progress in ancient times and why such aids to human frailty as false teeth and artificial limbs were in use long before spectacles, says the “Manchester Guardian.” Such optical instruments as were used by Greek and Roman scientists must ®have been primitive indeed if we are to judge from the following remarks of Aristitle:— “A person who shades liis eyes with his hand or who, looking through a tube, sees divers shades of colours neither hotter nor worse will nevertheless see further, as those who, for the observation of stars, go down pits and wells.” In support of the view that the ancients did not know how to make lenses it used to be said that Nero used t an emerald eyeglass through which s h f> looked at the circus games. It is now generally agreed, however, that what he used was an emerald mirror. The evidence on which the story is founded is a passage in the writings of Pliny, who says that the emperor looked at the game “in” an emerald, and he lias just been describing how polished emeralds could he used as mirrors. Just bow the emerald minor would add to his enjoyment of tiie spectacle is not quite easy to understand, for ancient mirrors were not very efficient aids to vision, if we are to accept St. Paul’s simile of seeing “in a mirror darkly.”