Devising magnetism Concepts and investigative practices Laura Georgescu Proefschrift voorgelegd tot het behalen van de graad van doctor in de wijsbgeerte Promoter: Prof. dr. Eric Schliesser Co-promoter: Prof. dr. Maarten Van Dyck Decaan: Prof. dr. Marc Boone Rector: Prof. dr. Anne De Paepe Faculteit Letteren & Wijsbegeerte Devising Magnetism Concepts and Investigative Practices Laura Georgescu Proefschrift voorgedragen tot het behalen van de graad van Doctor in de wijsbegeerte 2017 Table of contents Summary ................................................................................................................................. i Samenvatting .......................................................................................................................... v Acknowledgements ............................................................................................................... ix Introduction ............................................................................................................................ 1 A note about terminology .................................................................................................................. 4 Overview of the dissertation ............................................................................................................. 6 A note about methodology ................................................................................................................ 8 Part 1 Chapter 1: Historiographical Perspectives on the “Magnetical Philosophy” ....................... 11 1. The historical relevance of the magnetical philosophy ............................................................... 13 2. The historiography of the experimental method of the magnetical philosophy.......................... 18 3. Pumfrey’s account of the magnetical philosophy, and the sociology of scientific knowledge ... 21 4. The practice-centred historical account of the magnetic philosophy .......................................... 26 Conclusion ................................................................................................................................. 33 Chapter 2: From Attraction to Disponent ............................................................................. 35 1. The problems of magnetism as attraction ................................................................................... 37 1.1. Attraction and the localisation of magnetism ..................................................................... 38 1.2. De-localising magnetism .................................................................................................... 42 2. Gilbert’s two-layer matter theory ................................................................................................ 43 2.1. The genealogy of iron and lodestone .................................................................................. 43 2.2. Electric bodies and attraction .............................................................................................. 46 2.2.1. Electric bodies ............................................................................................................ 46 2.2.2. Attraction and causal unidirectionality ....................................................................... 49 2.2.3. Gilbert’s theory of gravity .......................................................................................... 49 TABLE OF CONTENTS 3. Gilbert’s magnetic philosophy and conceptual reform ............................................................... 52 3.1. The quest for “new and unusual” words ............................................................................. 53 3.2. From attraction to “coitio” .................................................................................................. 56 4. Conceptualising magnetism as disponent ................................................................................... 56 4.1. From magnetic power to the disponent power ................................................................... 57 4.2. The rule of the whole .......................................................................................................... 61 4.3. Magnetic movements through the disponent power .......................................................... 63 4.4. Objection: the disponent power as an occult quality? ........................................................ 65 5. From magnetism as alignment to magnetic rotation ................................................................... 66 5.1. Magnetic rotation ................................................................................................................ 66 5.2. Magnetic declination as rotation ......................................................................................... 67 5.3. The incompatibility between mapping and the attractional framework ............................. 71 5.4. Magnetism as disponent affords mapping practices ........................................................... 71 5.5. Full circle: from attraction to rotation. ............................................................................... 74 6. Disponent magnetism ................................................................................................................. 74 7. Conclusion .................................................................................................................................. 79 Chapter 3: Magnetical Philosophy and Spheres of Activity ................................................ 81 1. The emanationist conception of spheres of activity .................................................................... 83 1.1. The historiography of the emanationist theories................................................................. 83 1.2. Questioning spheres of activity in the emanationist theory ................................................ 84 1.3. Della Porta’s account of a sphere of activity ...................................................................... 85 1.4. Spheres of activity and internal limits ................................................................................ 87 2: Spheres of activity in mechanistic magnetism ........................................................................... 97 2.1. Digby’s atomistic magnetism ............................................................................................. 99 2.1.1 Atmospherical dynamics and Digby’s magnetic theory .............................................. 99 2.1.2. Digby’s spheres of activity. ...................................................................................... 103 2.1.3. Conclusion ................................................................................................................ 106 2.2. Descartes’ sphere of activity .................................................................................................. 106 2.2.1. Descartes’ mechanistic magnetism. ......................................................................... 106 2.2.2. The Cartesian sphere of activity ............................................................................... 110 2.2.3 Conclusion ................................................................................................................. 112 3. The orb of virtue as a property of an interaction ....................................................................... 112 3.1. Gilbert’s account of the magnetic force within the orb of virtue ...................................... 113 3.2. Barlow’s prioritisation of the interaction .......................................................................... 117 4. Concluding remarks .................................................................................................................. 122 Chapter 4: From Experiments to Diagrams to Concepts ................................................... 123 1. Studying visualisation in sciences............................................................................................. 124 2. Images in the magnetical philosophy ........................................................................................ 129 3. The Diagram of the movements in the magnetic orbes ............................................................ 134 3.1. The content of the Diagram of Orbes ............................................................................... 135 3.2. The depiction of the rule of alignment in the Diagram of Orbes ...................................... 137 3.3. Angular measurements of declination: missing links in the Diagram .............................. 140 TABLE OF CONTENTS 4. Gilbert’s dip–latitude correlation .............................................................................................. 144 4.1. The dip–latitude relation geometrically determined ......................................................... 144 4.2. The diagram of rotation of the magnetised needle ........................................................... 147 4.2.1 The Diagram .............................................................................................................. 149 4.2.2 The computation of the dip table and the diagram of the theoric .............................. 154 5. Conclusion ................................................................................................................................ 161 Chapter 5: Magnetic Inclination: Diachronic Change and Underlying Differentiation ..... 163 1.