Instrument and Influence: The Persisting Problem of Fair-Weather Electricity (1850-1930)

The analogy between lightning and the sparks drawn from electrical machines in 1752 has been heralded as a pivotal moment in the history of physics. That same year, Louis- Guillaume Le Monnier (1717-1799) found his electroscope rendered another phenomenon visible: ordinary air appeared to be electrical too. In this talk I explore this invisible, instrument-led problem of fair-weather electricity. I trace the changes in understanding between the first systematic, quantitative investigations in 1850 by Lord Kelvin, to C.T.R. Wilson’s 1930 model that brought together fair-weather electrification with lightning. I argue that shifts in understanding were mediated by both physical and metaphorical scientific instruments via the perspectives of different invisible electric quantities. I discuss how instruments were designed, used, improved, altered, and co-opted by different practitioners across the Northern Hemisphere to investigate atmospheric electrification, and how these devices reflected and shaped shifting criteria that were employed to measure different atmospheric-electric phenomena. Further, I show how using electrical instruments as “thinking tools” was central to many practitioners’ conceptualisations of the Earth-atmosphere system: metaphorical Leyden jars, capacitors, circuitry, and batteries were invariably invoked to carry significant explanatory weight. Through its material culture, I demonstrate how studying the electrical atmosphere also connects often disparate narratives in the history of physics across the long nineteenth century.

Katy Duncan is a PhD Student in the Department of History and Philosophy of Science at the University of Cambridge. She is a recipient of a Gerda Henkel Foundation Doctoral Scholarship and is a Royal Institution Freer Prize Fellow. Prior to her doctoral research, she obtained two master’s degrees: an MPhil in History and Philosophy of Science from the University of Cambridge and an MSci in Physics and Philosophy from the University of Bristol.