London
3rd December 1863
My dear Clausius
Your last kind letter1 has remained a long time unanswered. It would give me great delight to be your guest next year at the meeting in Zürich,2 but when I quit London I am so worn down—so utterly tired of science that I usually make my escape into the solitudes of the mountains. If however I go to Switzerland next year I should make an effort to visit you, but I am thinking of going to Norway.
I sent a little note to the Philosophical Magazine of November3 regarding Laplace’s correction of the theoretic velocity of sound. I cannot help thinking that what I have said has some foundation and that men have relied too much on the applicability of such experiments as those executed by Dulong4 in determining the specific heat of gases. For olefiant gas he found the ratio of the two specific heats to be 1.240. Now I should be disposed to conclude that if the gas demanded any interior work the ratio of the two specific heats, instead of being less than that found in the case of air, ought to be greater. I think that there is the very highest a priori probability against the concreteness of the number 1.240 as expressing the ratio of the two specific heats. Allowing air & olefiant gas to perform the same amount of exterior work the quantity of heat necessary to the performance of this work would in the two cases, if Dulong be right, be as 0.421:0.240; but inasmuch as air demands no interior work, and utilises in exterior work the entire excess of heat imparted to it, there must, if Dulong be right, exist in olefiant gas some magnitude of heat which it develops when expanding, and which enables a less amount of heat communicated from without to perform the same amount of work as that performed by expanding air:—This, to my mind is absurd.
I continue my experiments on Radiant Heat; the subject is exceedingly difficult; but I am attaining gradually a mastery over it: & I trust after some time that we shall know more of molecular physics than we do at present.
Give my kindest regards to Madame Clausius—& believe me
Yours ever | John Tyndall
RI MS JT/1/T/188
Your last kind letter: letter 2035.
the meeting in Zürich: the Naturforschende Gesellschaft, or Swiss Society of Natural Science, met in Zürich in July 1864. See letter 1906, n. 6.
Philosophical Magazine of November: J. Tyndall, ‘Note on Laplace’s Correction for the Theoretic Velocity of Sound’, Phil. Mag., 26 (1863), pp. 384–7.
Dulong: Pierre Louis Dulong (1785–1838), a French physicist and chemist. Amongst other researches, Dulong worked on the conduction of heat (CDSB). See P. L. Dulong, ‘Recherches sur la chaleur spécifique des fluids élastiques’, Annales de chimie et de physique, 41 (1829), pp. 113–59.
Please cite as “Tyndall2048,” in Ɛpsilon: The John Tyndall Collection accessed on