In the previous posts, I have introduced the problem of glass drops in the seventeenth-century natural philosophy, which I have further discussed in the case of Jacques Rohault’s Cartesian experimentalism and other Cartesian explanations provided by Henricus Regius and Nicolas-Joseph Poisson.
In the final post on this topic, I would like to refer to the explanation provided by an experimental philosopher par excellence, Robert Hooke (1635-1703).
Some of the earliest investigations of the drops took place in the Royal Society (see 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). Hooke was one of its most distinguished members and witnessed these inquiries from the very beginning (see Birch, Thomas. 1756. History of the Royal Society. Vol. I. London: A. Millar). After an initial report signed by Robert Moray in 1661, Hooke published his own observations in the celebrated Micrographia of 1665. He applies jointly direct observation, hypothetical thinking, and experiment in order to formulate an explanation “Of some Phenomena of Glass drops,” as it is said in the title of his seventh observation. As expected, glass drops and fragments of drops are examined through the microscope. Yet, Hooke notes the difficulties of his inquiry: “I could not find, either with my naked Eye, or a Microscope, that any of the broken pieces were of a regular figure, nor any one like another, but for the most part those that flaw’d off in large pieces were prettily branched” (p. 33). Trying to find the imperfection of glass, sets Hooke on a quest of successive trials, such as grinding the object in different parts and observe if there are new effects or immersing glass drops in various substances (e.g., Icthyocolla). Like in the prior cases of Rohault and Regius, Hooke complements his text with an illustration (see Fig. X at the bottom of this image):
The object is not only investigated empirically with various instruments, but the ‘conjectures’ formed in this process are further examined through analogy and transduction, which ports theoretical elements into Hooke’s analysis. Moreover, descending into the invisible structures of matter, forces him to leave the eye and the microscope and frame his explanation on top of other prior considerations about heat, fluidity, and matter in general. He concludes by ascribing the cause to the arrangement of particles of glass, which are gathered into a springy tension inside the drop.
It is not the place in this blog-post to go into the details of Hooke’s explanation of the phenomena produced by glass drops, but it is worth noticing that his experimental methodology overlaps with what I have presented in the post dedicated to Rohault. Theory and experimentation work together in finding the explanation, which, ultimately reduces to a mechanical model of the accepted theory of matter. These four cases of seventeenth-century natural philosophers interested in the study of glass drops make wonderful examples of how “new scientific objects” are discussed and explored with new methodological tools. I shall investigate this problem into a forthcoming article.