My dear Huxley

I was most deeply interested by the lecture at the Royal,² & was much vexed at being forced to retreat from my head aching so, & a pretty night I had afterwards! It is a horrid shame to trouble you, but I can hardly get subject out of my head, & am so very curious on one point, that I must beg for an answer on a point which I daresay came into the tail of the paper.— The point is, do you suppose if the fragments of ice did not after their innumerable fractures become united together by freezing;³ would the mass flow on? I suppose not, judging from the high angle of a talus of broken rocks though of course rock is far less brittle than ice. I presume the downward pressure could not be communicated through a fragmentary mass, just as you cannot push out an inch of sand in a gun barrel, though you could easily push out a piece of loose sandstone—or again, I suppose Tyndall would have found it far more difficult with his screw to have pushed out granular salt out of his semi-ring-model, than the piece of solid ice⁴ —or again I presume a scaffold pole would slide lengthways down a slope, down which a pile of fragments of wood would not slide.— Do tell me whether this is correct, for it seems to me quite beautiful if the freezing of the brittle ice, accounts for its filling all inequalities, its apparent solidity, & its flowing motion.—

By the way Tyndall ought to explain for ignoramuses how he knows that the ice freezes together & not merely coheres, like two pieces of wet glass— I do not understand how the non-coherence of snow or ice under a freezing temperature explains this; for it would be dry & so would not cohere; nor could I understand how he distinguishes the pillars or pinnacles (if I understand rightly) by which the pieces of Wenham ice were united, from preexisting ice thawed away.⁵ But I daresay all this is made clear in paper. The point which I want to know is the previous one, whether or not the freezing of the fragments together & the consequent easy transmission of force in one direction, is the cause of the flowing or sliding movement of the glaciers.—⁶

I never heard a more interesting paper than the part, which I did hear.— Forgive me for being so troublesome

Ever yours | C. Darwin