Editing Cavendish:Maxwell and The Electrical

Researches of Henry Cavendish

Isobel FalconerSt Andrews

ICOHP, Cambridge, Sept 2014

Please attribute Isobel Falconer . Except where otherwise stated,this work is licensed under a Creative Commons BY-SA 4.0 International License.

The Cast

What to include?1771 paper: An attempt to explain some of the principal

phaenomena of electricity by means of an elastic fluid

1776 paper: An account of some attempts to imitate the effects of the torpedo

MS of an extended work on the elastic fluid theory

MS methodical account of experiments bearing on the theory of electricity

Daily record of experiments on– Electrostatics (capacities of systems of conductors of various

shapes)– Inverse square law experiment– Electrical properties of non-conductors– Conductivity of solutions (related to torpedo)

How to represent it?

Harris, 1867, Treatise on Frictional Electricity

Maxwell, 1879, Electrical Researches of Henry Cavendish

No charge inside a conductor

Harris, 1867, Treatise on Frictional Electricity

Maxwell, 1879, Electrical Researches of Henry Cavendish

What to comment on? – electrical theory‘The leading idea which distinguishes…Cavendish from…his predecessors… is the introduction of the phrase “degree of electrification”…which…is precisely equivalent to what we now call potential’(Maxwell, 1879, Introduction to ER)

Photo by Isobel Falconer

‘His measurements of capacity will give us some work at the Cavendish Lab., before we work up to the point where he left it’ (Maxwell to Garnett, July 1874)

Electrical properties of non-conductors

Below: Maxwell’s comparison of Cavendish’s data

Left: Cavendish’s theory of (non)conduction in glass

Conductivity of salt solutions - Ohm’s law

OOO

Right: Maxwell, 1879 Plan of an experiment on the physiological effect of an induction current (for plan see Harman, Scientific Letters and Papers of James Clerk Maxwell, vol 3, (Cambridge: CUP, 2002) p769)

Conductivity of salt solutions -physiology

Above: Cavendish, experiments with the artificial torpedo

Conclusions

• Maxwell’s Electrical Researches of Henry Cavendish can be read as a move in the struggle to establish professional mathematical physics– A British and experimental genealogy

• Maxwell’s preoccupations were with:– evidence for his electromagnetic theory – furthering the ‘doctrine of method’

• Maxwell inverted Cavendish’s bodily methods, extending electromagnetic theory to investigations of the body

Credits & References• Henry Cavendish, By George Wilson [Public domain], via Wikimedia Commons• William Cavendish, 7th Duke of Devonshire, By Herbert Rose Barraud ([1]) [Public

domain], via Wikimedia Commons• James Clerk Maxwell by G. J. Stodart [Public domain], via Wikimedia Commons• William thomson lord kelvin at the age of twenty two" by Unknown [Public

domain], via Wikimedia Commons• Maxwell & McAlister’s inverse square law apparatus, in the

museum at the Cavendish Laboratory. Photo by Isobel Falconer licensed under a Creative Commons BY-NC-SA 4.0 international license

• William Snow Harris, A Treatise on Frictional Electricity, ed by C. Tomlinson (London: Virtue, 1867)

• Henry Cavendish: The Electrical Researches of the Honourable Henry Cavendish, ed. J. Clerk Maxwell, (Cambridge: University Press, 1879).

• Peter Harman, Scientific Letters and Papers of James Clerk Maxwell, vol 3, (Cambridge: CUP, 2002)