“Ha!” exclaimed the Professor, again smiling blandly, “there you have touched what once was, and, to some philosophers it seems, still is, the great difficulty. By some great men it has been held that glacier ice is always in a partially soft, viscid, or semi-fluid condition, somewhat like pitch, so that, although apparently a solid, brittle, and rigid body, it flows sluggishly in reality. Other philosophers have denied this theory, insisting that the ice of glaciers is not like pitch, but like glass, and that it cannot be squeezed without being broken, nor drawn without being cracked. These philosophers have discovered that when ice is subjected to great pressure it melts, and that, when the pressure is removed, the part so melted immediately freezes again—hence the name regelation, or re-freezing, is given to the process. Thus a glacier, they say, is in many places being continually melted and continually and instantaneously re-frozen, so that it is made to pass through narrow gorges, and to open out again when the enormous pressure has been removed. But this theory of regelation, although unquestionably true, and although it exercises some influence on glacier motion, does not, in my opinion, alone account for it. The opinion which seems to be most in favour among learned men—and that which I myself hold firmly—is, the theory of the Scottish Professor Forbes, namely, that a glacier is a semi-fluid body, it is largely impregnated throughout its extent with water, its particles move round and past each other—in other words, it flows in precisely the same manner as water, the only difference being that it is not quite so fluid; it is sluggish in its flow, but it certainly models itself to the ground over which it is forced by its own gravity, and it is only rent or broken into fragments when it is compelled to turn sharp angles, or to pass over steep convex slopes. Forbes, by his careful measurements and investigations, proved incontestably that in some glaciers the central portion travelled down its valley at double or treble the rate of its sides, without the continuity of the mass being broken. In small masses, indeed, glacier-ice is to all appearance rigid, but on a large scale it is unquestionably ductile.”
“Has the theory of regelation been put to the proof?” asked Lewis, with a degree of interest in glaciers which he had never before felt.
“It has,” answered the Professor. “An experimentalist once cut a bar of solid ice, like to a bar of soap in form and size, from a glacier. To this an iron weight of several pounds was suspended by means of a very fine wire, which was tied round the bar. The pressure of the wire melted the ice under it; as the water escaped it instantly re-froze above the wire; thus the wire went on cutting its way through the bar, and the water went on freezing, until at last the weight fell to the ground, and left the bar as solid and entire as if it had never been cut.”
“Well, now,” said Captain Wopper, bringing his hand down on his thigh with a slap that did more to arouse Mrs Stoutley out of her languor than the Professor’s lecture on glacier ice, “I’ve sailed round the world, I have, an’ seen many a strange sight, and what I’ve got to say is that I’ll believe that when I see it.”
“You shall see it soon then, I hope,” said the Professor, more blandly than ever, “for I intend to verify this experiment along with several others. I go to the Mer de Glace, perhaps as far as the Jardin, to-morrow. Will you come?”
“What may the Jardang be?” asked the Captain.
“Hallo! monkey, what’s wrong?” said Lewis to Emma, referring to one of the undertoned safety-valves before mentioned.
“Nothing,” replied Emma, pursing her little lips till they resembled a cherry.
“The Jardin, or garden,” said the Professor, “is a little spot of exquisite beauty in the midst of the glaciers, where a knoll of green grass and flowers peeps up in the surrounding sterility. It is one of the regular excursions from Chamouni.”
“Can ladies go?” asked Lewis.