Rendering Magnetism Visible: Diagrams and Experiments Between 1300 and 1700

Abstract

Human beings can neither see nor feel magnetism, although its effects can be made manifest to sense experience through experiments. Since antiquity, philosophers have therefore often viewed magnetism as an “occult” force, for whose manifest effects a hidden cause had to be sought. Around 1300, scholars began to address the seemingly occult nature of magnetism not only through experimental investigation but also visually, attempting to represent experimental results in diagrams. Historical research on diagrams has been fairly negligent about the relation between diagrams and scientific practices, including experiments. This paper will try to redress the balance, by focusing on diagrams in manuscripts and printed texts between 1300 and 1700 that were produced in response to magnetic experiments. It will be argued that naturalistic and geometrizing forms of representation were combined in order to render experiments with magnetism understandable, replicable, and meaningful. This resulted in a visual style of diagram that oscillated between the abstract representation of invisible entities or powers and the concrete and performative depiction of actual objects or operations.