[[Figs. 45] and [46] are from sketches made on the Furgge Glacier.—L. C. T.]
FOOTNOTES:
[A] In reply to a question in connexion with this subject, General Sabine has favoured me with the following note:—
"My dear Tyndall,
"It was in the summer of 1841, at the Lower Grindelwald Glacier, that I first saw, and was greatly impressed and interested by examining and endeavouring to understand (in which I did not succeed), the veined structure of the ice. I do not remember when I mentioned it to Forbes, but it must be before 1843, because it is noticed in his book, p. 29. I had never observed it in the glaciers of Spitzbergen or Baffin's Bay, or in the icebergs of the shores and straits of Davis or Barrow. I feel the more confident of this, because, when I first saw the veined structure in Switzerland, my Arctic experience was more fresh in my recollection, and I recollected nothing like it.
"Veins are indeed not uncommon in icebergs, but they quite resemble veins in rocks, and are formed by water filling fissures and freezing into blue ice, finely contrasted with the white granular substance of the berg.
"The ice of the Grindelwald Glacier (where I examined the veined structure) was broken up into very large masses, which by pressure had been upturned, so that a very poor judgment would be formed of the direction of the veins as they existed in the glacier before it had broken up.
"Sincerely yours,
"Edward Sabine.
"Feb. 20, 1860."
[B] In a letter to myself, published in the 17th volume of the 'Philosophical Magazine,' Professor Forbes writes as follows:—"In 1846, then, I abandoned no part of the theory of the veined structure, on which as you say so much labour had been expended, except the admission, always yielded with reluctance, and got rid of with satisfaction, that the congelation of water in the crevices of the glacier may extend in winter to a great depth."