June 1 1859
My Dear Mr Tyndall,
Having occasion to write an Article on Glaciers, I have cursorily read your papers,1 and those of Mr Huxley on the subject,2 and also Prof[esso]r Forbes’s Occasional Papers just published.3
I do not fully comprehend what the Professor (p. XVI) calls your theory,4 and therefore you would oblige me much if you could, in a few sentences, describe it, in order that I may study the evidence of it as given in your paper.
I am anxious to know the optical structure of the ice which forms the blue veins, in order to be able to judge whether it is formed from the nevé5 by pressure, or from the slow action of corporeal forces, as takes place in the decomposition of bodies such as glass & circular crystals which, in the course of time, return into their elements;—or by traction, as explained in one of my late papers in the Edin. Transactions.6
I would like also to know what is the optical structure of the solid Ice produced by pressure in your experiments. Is the axis of Double refraction parallel to the direction of the force? or does the ice exhibit the same effect that is produced by the compression of glass, and crystals that have a feeble double refraction.
I observe that Profr. Forbes regards your researches as confirming his theory. I am,
my Dear Mr Tyndall, | Ever Most Truly yrs. | D Brewster
Edin. 42 Charlotte Square | June 1st 1859.
P.S. My address after today is St. Andrews.
RI MS JT/1/B/128
RI MS JT/1/TYP/1/159
read your papers: see for example John Tyndall and Thomas Huxley, ‘On the Structure and Motion of Glaciers’, Phil. Trans., 147 (1857), pp. 327–46; John Tyndall, ‘On some Physical Properties of Ice’, Phil. Trans., 16 (1858), pp. 333–56.
those of Mr Huxley on the subject: likely refers to John Tyndall and Thomas Huxley’s cowritten article, see n. 1.
Prof[esso]r Forbes's Occasional Papers just published: Forbes’s book Occasional Papers on the Theory of Glaciers (Edinburgh: Adam and Charles Black, 1859).
what the Professor (p. XVI) calls your theory: refers to Forbes’s Occasional Papers, where he outlined his perception of Tyndall’s theory of glacial motion as one of fracture and regelation in comparison with his own, the viscous theory of glacial motion. See also letter 1594.
nevé: the hardened snow found on glaciers (OED).
as explained in one of my late papers in the Edin. Transactions: ‘On the Production of Crystalline Structure in Crystallised Powders, by Compression and Traction’, Transactions of the Royal Society of Edinburgh, 20 (1853), pp. 555–9.
Please cite as “Tyndall1620,” in Ɛpsilon: The John Tyndall Collection accessed on