One of the new ‘scientific’ objects that captured the attention of the seventeenth-century French and British experimentalists is what they call a ‘glass drop’: the result of dropping a bit of incandescent glass into a bucket of cold water. Peculiar to this object was its solidity, which was contrasted with the very minute fragmentation of glass that was produced when the drop was finally destroyed.
A representation of the glass drop can be observed in the following illustration from Jacques Rohault’s Traité de physique (1671).
This is the first post of a series discussing some seventeenth-century attempts to explain the properties of glass drops. Considered as one of the most intriguing objects, glass drop became an interesting item of study for many natural philosophers, including Robert Boyle, Jacques Rohault, Henricus Regius or Robert Hooke. As its name suggests, the object was made of glass and its peculiar shape intrigued as much as its apparently contradictory properties. On the one hand, the glass drop was found very difficult to break when it was pressed on the large size of the drop. On the other hand, its tail was very easy to fracture, which produced the blow of the drop with a loud noise.
A modern replica of the phenomena – starting from the production process of the drop and continuing with an exemplification of the two properties described above – is possible to watch online on the website of the Corning Museum of Glass (see http://www.cmog.org/video/prince-ruperts-drop): http://youtu.be/6V2eCFsDkK0.
The glass drop became philosophically interesting only in the seventeenth century. References to its structure and properties appeared almost at the same time in several places of Europe. The drop had also different names: larme de verre, lacryma Batavica, chymical glass, Prince Rupert’s drop, vitrae lacrymae, globuli vitrei, Batavian tears, etc. Its origins are still controversial, but it is commonly held that it came from either German lands or the Dutch provinces. I shall not try in these blog-posts to discuss the origins of this object or to attempt to correct some misconceptions about who has the priority in the philosophical investigation of the drop (an overview of these problems is in Brodsley, Laurel, Charles Frank, and John Steeds. 1986. “Prince Rupert’s Drops.” Notes and Records of the Royal Society of London 41 (1) (October): 1–26.). Rather, by looking at some of the early discussions and explanations of the phenomena produced by glass drops, I would like to suggest that early modern authors were forced to tackle the problem in a manner that included both theoretical and experimental examinations. This makes the glass drop case important for any discussion about the sources of knowledge in early modern philosophy, complicating the traditional divide between Rationalists and Empiricists and shading a new light on other more recent attempts to use actor-category terms, such as experimental and speculative (see the research project on Early Modern Experimental Philosophy at the University of Otago: https://blogs.otago.ac.nz/emxphi/the-project/).
In the next post, I shall discuss Jacques Rohault’s explanation of the phenomena.