Origins of the Sextant

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July-August 2019

Volume 107, Number 4
Page 195

DOI: 10.1511/2019.107.4.195

To the Editors:

I know little of artistic representations of Islamic science, so I was interested in learning more from the article “Forging Islamic Science” by Nir Shafir (Arts Lab, May–June). I found the author’s references to sextants in 16th-century miniatures jarring because I thought sextants were invented circa 1730 by Thomas Godfrey, an American optician and inventor. I did some research, and though I did not find any claims to invention earlier than 1730, there were indications in the writings of 16th-century English barrister and explorer Bartholomew Gosnold that such an instrument existed during his lifetime. However, there did not seem to be an early enough mention of sextants for the reference in the article.

Does Shafir’s use of the term sextant in the article refer to generic astronomical instruments, or to actual sextants—or is it erroneous?

John Crowe
Rockville, MD

Dr. Shafir responds:

Istanbul University Library / Istanbul, Turkey / Bridgeman Images

When researching for this article I investigated exactly what the object depicted in the illustration of the Istanbul observatory of Taqi ad-Din might be (right), including consulting with several experts on astronomical instruments from the premodern Middle East. In sum: Yes, the sextant as a navigational instrument was developed in the 18th century, but the sextant as an astronomical instrument has been around for much longer. It was usually built into a wall and then onto a large, stable frame.

Part of the confusion is that whatever is being held by the person in the illustration is not terribly clear, even to experts. The late historian of science John North wrote in his book Cosmos: An Illustrated History of Astronomy and Cosmology that it is an incorrectly drawn triquetrum, but other illustrations from the same observatory depict the triquetrum as being much larger. It could be an unnamed instrument for measuring vertical angles, but that would require it to be bolted into a horizontal position. There seems to be an instrument for that purpose on the table on the right hand side in the picture.

My sense is that the instrument the man in the upper left of the miniature is using is a sextant, possibly drawn without a frame. Though of course I’m happy to be proven wrong about it.