Chapter 1.

Early History of the Lens:

The first use of a lens is a bit of a mystery, but it's now believed that use of lenses is more modern than previously thought.

This chapter should give some insighs on how optical theory developed making microscopy possible.

The Lanyard Lens:

The above is the famous "Lanyard Lens" discovered at Nimrod by Lanyard, and datable to 721-705 BC. This was long thought to be the first example of a plano-convex lens. In the last century, however, studies of this object have shown that the curved surface is actually faceted, and not rounded, as one would have done to make a lens. Secondly, cloudy striae within the stone, which add an aesthetic quality, make it a poor magnifier. It is now generally agreed that this stone was actually just an ornament which fell away from it's mounting. It's now thought that lenses were not used nearly so long ago.

Ancient Writings of Optics

Several ancient manuscripts give us datable evidence of the state of refraction and optics throughout the ages.

2nd Century BC: Claudius Ptolemy:Described a stick appearing to bend in a pool of water, and accurately recorded the angles to within 1/2 degree for this relationship. He then very accurately calculated the refraction constant of water.
1st Century AD: Seneca: Described actual magnification by a globe of water. He wrote the following: "Letters, however small and indistinct, are seen enlarged and more clearly through a globe of glass filled with water."
962-1038 AD: Arabian Scholar Alhazen: Wrote the first major optical work Opticae Thesaurus discussing not only optical principles, but described the anatomy of the eye, and how the lens of the eye focuses an image on the retina.
1267 AD Bacon Wrote definite descriptions of simple magnification in his Perspectiva of 1267: "Great things can be performed by refracted vision. If the letters of a book, or any minute object, be viewed through a lesser segment of a sphere of glass or crystal, whose plane is laid upon them, they will appear far better and larger.

While the above exerpts give a glimpse at optical knowledge in the past, it's important to realize that this knowledge was likely confined to the learned scientists and philosophers. It wasn't until the invention of spectacles that optics came into common use.

Early Evidence of Spectacle Use:

It has been said that spectacles were in use in China well before they were known in the West. However, studies of early Chinese spectacles show that often the lenses were planar, without corrective abilities, and people may have actually used these colored glasses for cosmetic purposes rather than for astigmatism.

There is one very early description of an isolated use of spectacles. Pliny the Elder wrote the following in 23-79 A.D.:

"Emeralds are usually concave so that they may concentrate the visual rays. The Emperor Nero used to watch in an Emerald the gladatorial combats."

This quote appears to be the first description of using a monacle for correcting short-sighted vision. Strangely, even though this must have worked quite well, and many people must have read this passage, there is no other evidence of spectacle use for over twelve centuries.

The Invention of Spectacles:

The modern reinvention of spectacles occurred around 1280-1285 in Florence, Italy. While it's uncertain who the inventor was, it is quite clear that spectacles quickly took hold into common use in that city, and use of them spread outward to the rest of the known world in just a few years. Considering the large percentage of people with visual problems, it's not difficult to understand why there was such enthusiasm.

Strangely, it's not certain who in Florence made the first spectacles. Some give credit to a nobleman named Amati who died in 1317. It has been said that he made the invention, but told only a few of his closest friends.

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