Royal Observatory, Greenwich, 1856 March 8
Dear Sir
I have to present to you my thanks for two papers1 which reached me this morning. I ought long ago to have acknowledged a copy of your quarto Royal Society paper,2 and intended to do so, but I suppose that interruptions put it out of my thoughts.
My concerns with magnetism, especially in Gauss’s3 processes for absolute measure,4 and in the investigation of the angular disturbances of compasses, have all been of accurate character. They have all implied the application of the ordinary rules of mechanics by means of the severest numerical calculations. And the exactness of the representation of the phenomena by the calculation, in various ways, has produced on me a distinctness of conviction that magnetism (I should say paramagnetism) under all circumstances acts on calculable mechanical principles, such as can hardly be felt without going through those steps.
It has been a matter of no small grief to me to find that, till a comparatively late time, a totally different theory, a theory of extreme vagueness,5 has been advocated by the highest authority.
And now it is a matter of great satisfaction to me to find that, in all your investigations and explanations applying to diamagnetism, you have reduced all to a mechanical and calculable form.
I conceive that the position of the science is now very greatly altered, to an extent far beyond that to which your investigations ostensibly apply.
I am, dear Sir, | Very faithfully yours | G B Airy
Professor Tyndall
RI MS JT/1/A/28
Handwritten Copy: Airy Papers, MS RGO.6/694
two papers: Offprints of Tyndall’s recently-published papers, one of which was clearly ‘On the Relation of Diamagnetic Polarity to Magnecrystallic action’, Phil. Mag., [4] 11 (February 1856), pp. 125–37.
quarto Royal Society paper: J. Tyndall, ‘Further Researches on the Polarity of the Diamagnetic Force’, Phil. Trans., 146 (1856), pp. 237–59.
Gauss’s: Karl Friedrich Gauss (1777–1855), German mathematician, astronomer and physicist.
absolute measure: In 1832 Gauss established absolute units of distance (millimetre), mass (milligram) and time (second) in Intensitas vis Magneticae Terrestris ad Mensuram Absolutam Revocata (Sumtibus Dieterichianis: Göttingae, 1833), one of the last scientific works to be published in Latin.
a theory of extreme vagueness … advocated by the highest authority: Airy was referring to Faraday and his field theory. It was the simple mechanical couples and calculability of Tyndall’s work on magnetism that Airy (and later Herschel) liked as opposed to what even Tyndall referred to as Faraday’s “misty” concept of a “field”. See Tyndall’s earlier comment on Faraday’s lines of force in letter 1152.
Please cite as “Tyndall1202,” in Ɛpsilon: The John Tyndall Collection accessed on