Malahide1 Ireland | 15th Sept[embe]r 1864
My dear Tyndall,
Reading your paper (5th Memoir)2 for press recalls to my mind the importance, as it seems to me, of instituting experiments to determine whether we can fairly deem the radiating surface of the lamp-black coating of a Leslie’s cube3 containing water at 212o to be really at 212o. Were it so, it seems to me that the relative deportment of chloroform and iodide of methyl with lampblack4 and heated platinum is just the reverse of what we should have expected. For as lampblack transmits the low rays well, it ought to emit them badly, and therefore it seems to me that the radiation from lamp-black at 212o ought to be related to that from platinum at 212o, as to quality, as the radiation from a higher to that from a lower source.
I suspect that from the excellent radiating and bad conducting power of lampblack, the really radiating layer is considerably below 212o in spite of the small thickness of the whole stratum.
By the bye how do you get over this difficulty as to a necessary physical connexion between conduction and radiation? We know of plenty of bodies that are highly transparent with regard to light of one kind A, and highly opaque with regard to another kind B, differing, it may be, not greatly in refrangibility; and the absolute identity of the laws of radiant heat and light lead us to suppose that there are probably bodies similarly related to two kinds of heat A', B', both it may be invisible. Such a body must be a very bad radiator for heat of the kind A', and a very good one for heat of the kind B'. What sort of a conductor is it?
Whether such a body exists or not seems to me of small moment. Unless we reject the identity of laws of light and radiant heat, we may imagine such a body to exist without any violation of existing laws.
Yours very truly | G. G. Stokes
P.S. At p. 361 I have inserted the words “subsequently to the presentation of this Memoir” after the words.
The change of quality produced …. by the introduction of a platinum spiral …. My assistant, Mr Barrett5
Please write to the printers to say if you approve as I desired them to insert subject to your approval. If my words <herafter LT Typescript only> won’t do please alter them to what will be right.
RI MS JT/1/S/237
RI MS JT/1/TYP/4/1396
Malahide: a coastal settlement in Fingal, County Dublin, Ireland.
your paper (5th Memoir): see letter 2097, n. 3. See also letters 2099, 2112, 2114, 2115, 2117, and 2119.
Leslie’s cube: an instrument invented by John Leslie (see letter 2012, n. 2) for measuring variations in thermal radiation emitted from different surfaces at the same temperature (see J. Leslie, An Experimental Inquiry Into the Nature and Propagation of Heat (London: J. Mawman, 1804), pp. 6–8).
lampblack: a pigment consisting of almost pure carbon in a state of fine division; made by collecting the soot produced by burning oil or gas (OED).
Mr Barrett: William Barrett.
Please cite as “Tyndall2136,” in Ɛpsilon: The John Tyndall Collection accessed on