To John Frederick William Herschel 23rd Nov. 1861
Royal Institution of Great Britain | 23rd Nov. 1861
Dear Sir John
Let me say one word more1 & then I will not pester you until this matter is completely investigated.
When I said that the effect I observed was equivalent to a radiation of cold by the moon I entertained no idea that there was any such radiation—but the effect was such as if the moon radiated cold.
From the astronomer Royal’s lecture at Manchester2 it might be inferred that the atmosphere extended enormously beyond the limits which you have assumed—but then you would urge the tenacity of the air at those distances—I will here only say that at present I am able to measure with certainty the radiation of a particular description of vapour possessing the 
of an atmosphere of tension. As soon as my work is complete I will give you a fuller account of my experiments.
Yours most truly | John Tyndall
RS HS 17.390
Let me say one word more: Tyndall is here replying to Herschel’s response to his experiments on lunar radiation. See letters 1830 and 1831.
the astronomer Royal’s lecture at Manchester: George Biddell Airy (1801–92), the Astronomer Royal, was President of Section A (Mathematics and Physics) during the meeting of the BAAS at Manchester, September 1861.
Please cite as “Tyndall1832,” in Ɛpsilon: The John Tyndall Collection accessed on