Experiments in the Making: Instruments and Forms of Quantification in Francis Bacon’s Historia Densi et Rari

Abstract

Abstract The Historia densi et rari, published posthumously in 1658, is probably Francis Bacon’s most complex natural and experimental history. It contains observations and experimental reports, quantitative estimates and tables, and theoretical and methodological considerations, in a structure which has never been fully investigated. I provide here a fresh reading of this text from the perspective of scientific practices. I claim that Historia densi et rari represents a quantitative and instrumental investigation assembled with the help of Bacon’s philosophy of experiment as developed in the Novum organum. I first discuss the role played in the Historia densi et rari by the various instances of special power in delineating the object of research. I then analyze the ways in which a special class of instances of special power, the “mathematical instances,” are used in the Historia densi et rari to make the inquiry both more precise, and more abstract. Bacon used mathematical instances to transform traditional recipes of pneumatics into quantitative, more general investigations into universal motions and processes. Finally, I discuss two examples of scientific practice at work: the attempt to use instruments to gradually define and clarify “proper” (i.e., scientific) notions of “rarefaction” and “condensation,” and the redefinition of a metaphysical concept (plica materiae) in instrumental and operational terms.