ON THE TEMPERATURE OF FOAM. | To Dr. Tyndall, F.R.S. &c.
Museum of Practical Geology, | May 4, 1857.
DEAR SIR,
YOUR remarks in the last Number of the Philosophical Magazine,2 on the Temperature of Foam, recall to my mind an observation of a similar kind made by myself and my friend, Mr. James Simpson,3 jun., when on a pedestrian excursion in Surrey in December 1855.
Our attention was arrested, on arriving at the last lock on the river Wey,4 at the distance of about half a mile from the point where it empties itself into the Thames,5 by the production of an extraordinary amount of foam, in consequence of the falling of the river over a weir.6
This foam was not only unusual in amount, but had a peculiar soapy appearance, and on dipping the hand into it was found to be quite warm: fortunately we had a thermometer with us, and were therefore enabled to measure the extent to which the temperature of the foam exceeded that of the water on which it was formed.
The temperature of the water was 42°·5 F., whilst that of the foam was 45°, so that the foam was 2°·5 warmer than the water. The thought immediately struck me that its warmth must be due to the air enclosed within it; and if such were the case, it should have a temperature intermediate between that of the water and the air. And such really was the case; for the air, though feeling very cold in consequence of a strong easterly wind blowing, did not fall below 50° F.
I may state that the phaenomenon appearing to me very curious at the time, considerable care was devoted to the observation of these temperatures, the thermometer being allowed to remain long enough in each medium to become quite stationary.
I am, Sir, | Yours respectfully, | HENRY M. WITT, F.C.S., | Assistant Chemist to the Government | School of Mines.
H. M. Witt, ‘On the Temperature of Foam’, Phil. Mag., 13 (1857), pp. 467–8.
Henry Witt: Henry Matthew Witt (c.1833–58), a pharmaceutical chemist and assistant chemist at the Government School of Mines, who had studied with Hofmann at the Royal College of Chemistry. See ‘Melancholy Death of Mr. Henry Matthew Witt’, Pharmaceutical Journal, 18 (1858), p. 46.
YOUR remarks in the last Number of the Philosophical Magazine: J. Tyndall, ‘Remarks on Foam and Hail’, Phil. Mag., 13 (1857), pp. 352–3.
Mr. James Simpson: possibly James Liddell Simpson (1829–89), eldest son of waterworks engineer James Simpson (1799–1869). In 1857 James Simpson junior joined the family firm Simpson & Co. to work on improvements of pumping machinery. D. G. M. Roberts, ‘Simpson, James Liddell’, in P. S. M. Cross-Rudkin, et. al. eds, Biographical Dictionary of Civil Engineers in Great Britain and Ireland, 3 vols. (London: Thomas Telford Publishing, 2008), vol. 2 (1830–90), p. 716.
the river Wey: an 87-mile tributary of the River Thames.
the Thames: the River Thames, a 215-mile river in southern England, passing through London.
weir: a dam, of which there are various forms, constructed on the reaches of a canal or navigable river, to retain the water and regulate its flow (OED).
Please cite as “Tyndall1389,” in Ɛpsilon: The John Tyndall Collection accessed on