21st Dec. 1861
My dear Mr. Stokes,
I have a paper ready to be placed in your hands:1 I lecture on the subject of it on Friday evening January 17th at the Royal Institution.2
Last year it was not deemed necessary to bring my paper forward at the Royal Society before it formed the subject of my Friday evening lecture. But then it was the Bakerian Lecture3 & that may make a difference.
Would you kindly inform me what the arrangement will be4 this year so that I may hold myself prepared for it?
I had no opportunity of talking to you about the convection question but I see no escape from the conclusion that, with the same difference of temperature, the velocity of the particles of air at half an atmosphere of tension, is to the velocity at a whole atmosphere of tension is as 64: 34.
This retardation in the case of the denser gas I can refer to no other cause than internal friction.
I do not like to trust myself even in simple matters when I am hard pressed as I am at present—and I shd therefore be much obliged to you for your opinion on the following point:—Supposing two gases of the specific gravity S and S' at the common tension of 1 atmosphere to be allowed to stream thro’ a small aperture into a vacuum what will be the relative volumes discharged in a given time supposing the elastic force to have no resistance save the inertia of the gas itself to overcome—that is to say supposing friction internal & external to be entirely absent?
Yours very truly | John Tyndall
RI MS JT/T1397
a paper to ready to be placed in your hands: published as Tyndall (1862).
at the Royal Institution: Tyndall lectured on Friday 17 January at the RI on the subject of the transmission of heat through gases. Abstracted as J. Tyndall, ‘On the absorption and radiation of heat by gaseous matter’, Roy. Inst. Proc. 3 (1858–62), pp. 404–07.
Bakerian lecture: an annual lecture established through the bequest of Henry Baker FRS (1698-1774) and delivered by one of the Fellows of the Royal Society. Tyndall’s lecture was published as, Tyndall (1861). This was his second Bakerian lecture. Over his lifetime, Tyndall was invited to give four Bakerian lectures, more than anyone since.
What the arrangement will be: for Stokes’ response, see letter 1843.
Please cite as “Tyndall1842,” in Ɛpsilon: The John Tyndall Collection accessed on