During excavations of the ancient Assyrian capital of Kalkhu (better known as Nimrud, in Iraq) in 1850, archaeologist Austen Henry Layard found a piece of rock crystal buried under the ruins of the Northwest Palace's throne room.
It was under other pieces of glass that seemed to have been part of an object, perhaps wood or ivory, that had broken or disintegrated over the centuries.
With the glass bowls a rock crystal lens was discovered, with opposite flat and convex faces. The Assyrians did not know its characteristics, so it is the first example of magnifying glass and glass to burn. It was buried under a heap of fragments of beautiful opaque blue glass, apparently the enamel of some ivory or wooden object, which had perished.
—Austen Henry Layard, Discoveries in the Ruins of Nineveh and Babylon
Nimrud lens. Photo: The British Museum
It is a lens, crudely carved and slightly oval in shape, dated to the 8th century BC between 750 and 710 BC during the Neo-Assyrian period. It has a maximum diameter of 4.20 centimeters, and a thickness of between 4.10 and 6.20 millimeters. It has a focal length of about 12 centimeters, which makes it equivalent to a 3x magnifying glass.
The lens surface has 12 cavities opened during grinding, which may have contained naphtha or some other fluid trapped in the raw glass. Since it is made from natural rock crystal, it has not deteriorated significantly over time.
At the time of discovery, Layard immediately identified it as a lens, although he believed that the Assyrians did not know its optical properties, that is, to increase the size of things in sight, but used it to light fire. However, he also pointed out that some inscriptions he discovered at the same site were so small that they could have been made with the aid of a lens.
There is certainly no evidence that the Assyrians wore glasses, although many opticians who have examined the piece over the years believe that it was deliberately made as a lens. Given that its size fits perfectly in the eye socket, it would be a kind of monocle used by a scribe or a craftsman.
Photo: The British Museum
Others think that its optical properties are accidental, and that it is probably a decorative piece that would be embedded in furniture or other types of decoration.
The Italian Assyriologist and paleographer Giovanni Pettinato believed that this lens had been part of a kind of telescope, which would explain the Assyrians' knowledge of astronomy. However, the poor quality of the lens does not support this hypothesis.
But according to Pettinato, that the Assyrians represented the planet Saturn as a god surrounded by serpents suggests that this was their interpretation of the rings they saw (rather blurry) through the supposed telescope.
The hypothesis that they used the lens to light fire is supported by a similar object mentioned in the Epic of Ishtar and Izdubar (an early translation of the Gilgamesh poem, when all the fragments known today had not yet been discovered):
The King then rises, takes the sacred vessel, / And holds it up to the sun before the mass / of fuel waiting on the stacked altar. / Centered rays…bright fuel gilds / With a round spot of fire and swiftly / Upon the altar they coil, as they sing!
—Leonidas Le Cenci Hamilton, Ishtar and Izdubar IV
Artist’s impression of the palaces of Nimrud by Austen Henry Layard. Photo: Wikimedia
One of the last specialists to examine the lens, Dr. Ángel Tomás Camacho Garcia, from the Institute of Culture, Science and Technology of Galicia, maintains that the lens was set in a metal frame and that it was probably destined for a person with great power, for example King Sargon II, to correct his astigmatism.
Today it would be possible to go out and find someone who had a degree of astigmatism that would be perfectly corrected with Layard's lens. The problem is that such toroidal lenses for correcting astigmatism only began to be produced in Europe in the mid-19th century and only became available to the general public on an industrial basis around the year 1900. And yet here we have a lens that looks like it! to have been produced no later than the 7th century BC! Since we cannot assume that the Assyrians (or the workers who produced the lenses for them, since he could have been a foreign craftsman) had enough optical theory to be able to design and execute a toroidal lens on the basis of calculations, the point more conservative view and the safest, in the absence of any other evidence, is to conclude that the production of such a lens was executed by trial and error, on an empirical rather than theoretical basis. But even so, the achievement that a toroidal lens was developed nearly 3,000 years ago to correct an individual case of astigmatism cannot be underestimated.
—Ángel Tomás Camacho García, The Surprising Story of Layard's Lens , pp. 36-43
The fact that Layard found the lens in the throne room of the palace would therefore suggest that it was actually a monocle for Sargon II, who reigned between 722 and 705 BC.
Quartz lenses are known to have been used in Babylon, ancient Egypt and ancient Greece, but few have survived, and none are as old as the one at Nimrud. Therefore it is considered to be the oldest optical instrument found so far by archaeologists.
The Nimrud lens is kept in the British Museum, where it is not currently on display.
Nimrud lens at the British museum. Photo: Geni/Wikimedia
This article was originally published in La Brújula Verde. It has been translated from Spanish and republished with permission.
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