Edin. June /60
My dear Tyndall
My difficulty about publishing my letter to you1 is that I have not made up my mind whether my molecule Ice2 is
Recent analyses of the Hydrates of Barytes & Strontia by Bloxam3 would lead to the former view.
Hydrate of Barytes (readily got by boiling Crystd BaO1 NO5 with a solution of 2Eq. NaO) has remarkably the power of keeping in solution a supersaturated quantity of
corresponding to Ice—
Would two crystals of
regelate in such a solution?
Yours Sin[cere]y | Lyon Playfair
P.S. If you accept the proposal4 of the Phil. Inst. to lecture here in winter, I shall have a room at your service while you are in Edinburgh
RI MS JT/1/P/127
RI MS JT/1/TYP/3/994
my letter to you: letter 1702. Tyndall was asking Playfair about the properties of ice because of his research on glaciers, his idea of ‘regelation’ and therefore the importance of the behaviour of ice near its freezing point.
my molecule Ice: Playfair assumed a chemical distinction between ice and water to account for the behaviour of water as it reaches its freezing point. As water cools, its density increases, until at 4oC it starts to decrease. At the freezing point, unusually for a substance, ice is less dense than water, so it floats. Playfair argued that the formation and dissolution of a separate particle ‘ice’ in the water sample at low temperatures would account for the expansion below 4oC. The ‘freezing’ of water would be nothing more than ‘the separation of ice from a saturated solution of ice’. See Frederic Guthrie, ‘On Cryohydrates and Water of Crystallization’, in Conferences held in Connection with the Special Loan Collection of Scientific Apparatus, ed. Various, (London: Chapman & Hall, 1876), p. 99. See also letter 1702.
Bloxam: See Charles L. Bloxam, ‘On the crystallized hydrates of baryta and strontia’, Quarterly Journal of the Chemical Society of London, 13 (1861), pp. 48–50.
if you accept the proposal: see letter 1711.
Please cite as “Tyndall1719,” in Ɛpsilon: The John Tyndall Collection accessed on