[Sca-cooks] Farsighted lenses

[TerryDecker]

424 BCE?  That will be a a burning glass mentioned in Aristophanes "The 
Cloud."  That makes it a bi-convex lens, probably of glass but possibly of 
rock crystal.  The earliest known lens in the Layard lens, Assyrian rock 
crystal from roughly 1000 BCE.

A source that I really would like to see on this subject is Vincent Ilardi, 
Renaissance Vision from Spectacles to Telescopes from the American 
Philosophical Society.

Bear

-----Original Message----- 
From: Susan Lord Williams

http://en.wikipedia.org/wiki/Magnifying_glass states that “a magnifying 
devise” existed  in 424 BC. It does not specify whether it was glass, 
crystal or clear quartz. What is the difference? - It continues to state 
that “glass lenses” were produced in the Middle Ages. I assume that 
magnifying lenses were available.

Medieval Muslims, including those in Bagdad and Andalusia, worked with 
quartz and also they had a oops - glass or crystal factory (now that you 
question it I don’t know which) outside of Cordoba by the 9th century as 
Ziryab insisted that wine be drunk from glass  or crystal goblets. I don’t 
know enough about it to be able to say if they produced glass or crystal.

Do we have an optometrist amongst us who knows about the history of the 
development of lenses?