Royal Institution | 14th Nov. 1864
My dear Sir John,
I wish I was at liberty to write freely on some of the points raised in your last letter1 to me. But to my great regret this is not the case. Owing to one of those incidents2 which ruffle the calm flow of science, I have voluntary renounced the idea of making any thing known, for some considerable time, regarding the experiments which I have recently executed on the change of refrangibility of the extra red rays.
There are other points however on which I am at the liberty to speak. I have devoted some time to the examination of the extra-red region with a view to your own results. I have operated with rock salt prisms, with flint glass prisms (from Munich) and with hollow prisms possessing rocksalt sides and filled with bisulphide of carbon. As yet I have failed to obtain the maxima & minima which revealed themselves on your thermo-graph
From this I inferred that the maxima & minima were of atmospheric origin, and I thought they might be caused to appear by sending the beam, before analysis, through a thin layer of water. The experiment was very successful.
I have tried several other liquids in the same way, but hitherto with negative results.
I have also interposed a number of gases in the path of the beam, but without success. The absorption by both liquids & gases appears to extend uniformly over the extra-red space. I have not, however, yet done with the subject, and should anything positive arise I will at once let you know.
With regards to § 263 I would remark that all the rays from the platinum are absorbed by the lampblack on the face of the pile; and all of them are therefore converted into heat. It is the heat value (if I may use the term) of the rays which is given by the deflection.
The other points to which you refer shall receive due attention
Yours most truly | John Tyndall.
RS HS 395
RI MS JT/1/TYP/2/531
your last letter: letter 2186.
one of those incidents: this is in reference to a dispute between C. K. Akin and Tyndall regarding a paper on ray transmutation Akin wanted published in the Phil. Mag. Between November 1864 and 1865, Tyndall did not write or publish on the subject. The ordeal is discussed in detail in J. Tyndall, ‘On the History of Calorescence’, Phil. Mag., 29 (1865), pp. 218–31, For further discussion of the priority dispute between Tyndall and Akin, see letters 1925, 2075, 2076, 2079, 2114, 2162, 2167, 2168, 2170, 2173, the introductory essay for this volume and letters in the forthcoming ninth volume of The Correspondence of John Tyndall.
§ 26: see letter 2014, n. 2, and letter 2183.
Please cite as “Tyndall2177,” in Ɛpsilon: The John Tyndall Collection accessed on