22 Jan 2019 10:00am - 1:00pm Seminar Room 2, Department of History and Philosophy of Science, Free School Lane, Cambridge


This is a study day organized by the AHRC-funded project, Making Visible: The visual and graphic practices of the early Royal Society.


  • Dr Michael Korey, Curator at the Dresden State Art Galleries
  • Dr Tiemen Cocquyt, Curator at the Rijksmuseum Boerhaave 

The expert curators will introduce the most recent research on the materiality of historical optical instruments and their lenses, accompanied by hands-on sessions with replica instruments.  

This workshop is free and open to all, booking is recommended.


09:30 -10:00

Tea and coffee

10:00 - 11:30

New Light on Old Instruments – Recent Findings on the Optics and Materiality of Early Telescopes

Michael Korey Staatliche Kunstsammlungen Dresden & Tiemen Cocquyt, Rijksmuseum Boerhaave

A telescope serves as an easily recognizable scientific instrument, one with a readily understood purpose and construction. Or so it would seem. The talk will recount an intensive 3-month research expedition (with Marvin Bolt, curator at the Corning Museum of Glass) tracking down and optically measuring telescopic “incunabulae” in more than two dozen museums and private collections across Europe, which capped a decade of investigating the startling variety of early instruments. In addition to describing our methods, this richly illustrated and broadly accessible lecture will present selected key findings: the surprising quality of the oldest securely dated telescope, including interferometric analysis of its lenses; the discovery of the only two known examples of 17th-century Keplerian telescopes and their connection to painterly iconography; and the intersection of theory and craft practice in the lensmaking of Isaac Beeckman.

A hands-on session with replica telescopes for use in direct observation and solar projection (weather permitting) will follow the talk.

11:30 -12:00

Tea and coffee

12:00 - 13:00

Blown, Ground, Flame-Worked, or Dropped? Interrogating the Lenses of 17th-Century Simple Microscopes 

Tiemen Cocquyt Rijksmuseum Boerhaave & Michael Korey, Staatliche Kunstsammlungen Dresden

The single-lens (“simple”) microscopes made and used by Antoni van Leeuwenhoek in the years 1672 – 1721 have acquired iconic status in the history of 17th-century science for their role in fundamental microbiological discoveries. Yet surprisingly little is known with certainty about the composition and construction of the key component of the ten or so surviving instruments of this type: the tiny glass lenses mounted between thin metal plates, with a free aperture of only 1 mm or less. Were they ground, as Leeuwenhoek himself claimed, flame-worked, or produced by some other method? A combination of approaches – empirical trials with master glassworkers, innovative material analysis, and a re-examination of contemporary archival sources – leads us to question traditional accounts of these lenses. In particular, we look closely at the work of the Amsterdam regent Johannes Hudde (1628-1704), whose introduction in the 1660s of flame-worked, solid globular lenses, rather than the ground glasses of lenticular shape common until then, strikingly re-oriented Dutch microscopic activity. In what technological context did Hudde’s lenses emerge? How did the optical properties of his lenses differ from those of his predecessors? Did his lenses arise from practical experience, from developments in theoretical optics, or in a way that might be situated outside the optical tradition? While addressing these topics in the context of 17th-century glass technology, some points become clearer, new questions emerge, but the meaning of a contemporary “Dutch joke” remains to be resolved.

A hands-on observing session using replicated single-lens microscopes will follow the talk.  

13:00 - 14:00

Participants are cordially invited to a light lunch, to continue further conversation.

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