When in museums, we are accustomed to seeing the beautiful instruments of the Scientific Enlightenment constructed of gleaming brass. But, in an early example of recycling, five telescopes made from the metatarsal (foot) bone of a cow were discovered recently in Amsterdam. Dating to the 18th Century, over 100 years after the invention of the telescope and microscope, these small (8-14 cm long) telescopes are of surprising sophistication.
The largest of the recovered instruments is composed of two parts with a screw thread to join the pieces and contains a bone insertion thought to have functioned as an aperture stop. Their magnification, through paired lenses, is only about 3X which was weak compared with other telescopes of the day, and so they may have been used as opera glasses and seeing over relatively short distances.
Curiously, telescopes at this time would have been luxury items, therefore the buyer would be able to afford brass. So why cow bone? Perhaps simply as a curiosity? As a further question, two of these were found in historical cesspits (toilets), suggesting they may not have been highly valued.
These finding are published by Marloes J. Rijkelijkhuize in Volume 3 (November 2011) of The Journal of Archaeology in the Low Countries.