The Nimrud lens
The Nimrud lens or Layard lens is a 3000-year old piece of rock crystal, which was unearthed by Austen Henry Layard at the Assyrian palace of Nimrud, in modern-day Iraq. It may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight, or it may have been a piece of decorative inlay.
The lens is slightly oval, and was roughly ground, perhaps on a lapidary wheel. It has a focal point about 11 centimetres (4.5 in) from the flat side, and a focal length of about 12 cm. This would make it equivalent to a 3× magnifying glass...
The function of the lens is not clear, with some authors suggesting that it was used as an optical lens and others suggesting a decorative function. Assyrian craftsmen made intricate engravings, and could have used a magnifying lens in their work. The discoverer of the lens noted that he had found very small inscriptions on Assyrian artefacts which he suspected had been achieved with the aid of a lens. Italian scientist Giovanni Pettinato of the University of Rome has proposed that the lens was used by the ancient Assyrians as part of a telescope, and that this explains their knowledge of astronomy. Experts on Assyrian archaeology are unconvinced, doubting that the optical quality of the lens is sufficient to be of much use.
More at
Wikipedia.
A wonderful artifact, but this is only the tip of the iceberg concerning ancient optics and lenses. I heartily recommend scholar Robert Temple's book, “The Crystal Sun” (2000, Century, London). Quoting a bit of the sleeve notes:
ReplyDelete“Based on 33 years of research all over the world, . . . Robert Temple has reconstructed a wholly forgotten story: the story of light technology in ancient civilisation. It goes back at least to 2600 BC in Old Kingdom Egypt. . . . (and how the Egyptians) surveyed their pyramids and other structures with such uncanny precision; they used the equivalents of theodolites with lenses and . . . produce miniature carvings on gems, including some so small they are invisible to the naked eye altogether.”
The book has photos and reports of many such lenses in scattered museums, many of which are mis-identified. It's a big book with lots of details. Well worth it if you like things that change our view of ancient human civilization.