The Discovery of Ghijsbrecht Donckere’s Perpetuum Mobile: Visual Proof of the First Barometer?

Ghijsbrecht Donckere is sometimes associated with the invention of the barometer, based on two textual sources from about 1620. No visual record was known of Donckere’s instrument, which was referred to as a perpetuum mobile, until now. The rediscovery of a third source, and more importantly, the identification of his device on a contemporary painting, calls for a reassessment. The surroundings of the perpetual motion machine as represented in paint place this instrument at the intersection of natural philosophy and mechanical engineering. Donckere’s invention appears to be loosely based on Cornelis Drebbel’s perpetuum mobile (ca. 1607), and was commissioned by a courtly couple that was already partially informed about the hidden cause of motion of this machine. Nevertheless, the symbolic meaning of the object, rather than an understanding of its actual workings, is put on display. Donckere’s instrument is thus inextricably linked to one of the Aristotelian senses, and to concepts of astronomy and harmony, such as the primum mobile and musica universalis. Even though the textual evidence suggests that the device was at some point used to predict the weather, a reinterpretation particularly emphasizes the rhetoric of the time. The sources do not indicate that the effect of atmospheric pressure was already known. Taking these observations into account, the label of barometer does not seem applicable to Donckere’s perpetuum mobile. The newly revealed visual proof portrays the instrument instead as a collector’s item to be interpreted intellectually by an elite clientele in the early seventeenth century.