The Royal Society. | Burlington House | W. | Jan[ua]ry. 1. 1865
Dear Tyndall:
Be but reasonably prudent, and I trust you have as many years of usefulness and happiness before you, as your friends, amongst whom I am proud to number myself could wish you. Thanks on my wife’s1 part, as well as on my own, for your kind note.2
I have received a paper3 from H. de Schlagintweit4 on a subject which connects itself very closely with your pursuits. It is on Insolation in India and Thibet; measuring Insolation by the difference of the temperature shown by two precisely similar therm[omet]ers. one in the Sun & the other in the shade; interfering causes being as much as possible avoided in both cases; and the temperature observed as nearly as may be at the times of the maxima of each day. The general result is a connection of a very decided character manifested between the amount of Insolation and that of the relative humidity. The insolation is greatest where the amount of transparent aqueous vapour is greatest. The facts which are adduced are derived from a very large induction. The paper is so illegible in its latter part, & his discussion of the causes of this connection so immethodically stated, that I expect it will be necessary to request him to rewrite some parts of it:—But as far as I can at present apprehend his meaning, he ascribes the very high figure which the insolator attains when much aqueous vapour is present to the diminution of loss by radiation from the sun thermometer. He regards this as in full accordance with your recent researches
Have you experiments bearing on the question of the interception or non interception by transparent aqueous vapour of heat proceeding directly from the sun itself?
When I am better informed than at present of what H. de Schlaginweits mode of explanation really is, I shall be glad to resume the subject with you; but until his paper is made intelligible, in its reasonings as well as in its facts, one can scarcely reason upon them to any purpose.
Sincerely yours | Edward Sabine.
RI MS JT/2/10/323
RI MS JT/2/13c/1276
my wife’s: see letter 2157, n. 9.
your kind note: letter missing.
a paper: H. Schlagintweit, ‘Beobaehtungen über den Einfluss der Feuchtigkeit auf
die Insolation, in Indien und Hochasien’, Sitzungsberichte der Königl. Bayer. Akademie der Wissenschaften zu München, 2 (1864), pp. 216–46. See also H. Schlagintweit, ‘Numerical Elements of Indian Meteorology.—Series II. Insolation, and its Connexion with Atmospheric Moisture’, Roy. Soc. Proc., 14 (1865), pp. 11–2. In his work Meteorology of India: an analysis of the physical conditions of India, the Himálaya, western Tibet, and Turkistan (Leipzig and London: F. A. Brockhaus and Trübner & co., 1866), Schlagintweit mentioned Tyndall’s work as Sabine describes it in this letter (pp. 51–2).
H. de Schlagintweit: Hermann Schlagintweit (1829–82), an explorer of Central Asia, brother and fellow explorer of Adolf Schlagintweit (1829–1857). Together they produced a scientific study on the Alps between 1846–48. Later, on the recommendation of Alexander von Humboldt, they conducted studies of the Earth’s magnetic fields in the Himalayas.
Please cite as “Tyndall2210,” in Ɛpsilon: The John Tyndall Collection accessed on