Sir,
The following observation may interest a large class of the readers of The Times; I therefore send it to you to be disposed of as you think fit:
Many years ago Mr William Hopkins of Cambridge pointed to the state of the rocks over which glaciers had passed as conclusive evidence that these vast masses of ice move bodily along their beds. Those rocks are known to have their angles rasped off, and to be fluted and scarred by the ice which has passed over them. Such appearances, indeed, constitute the entire evidence of the former existence of glaciers in this and other countries, discussed in the writings of Venetz,1 Charpentier, Agassiz, Buckland,2 Darwin, Ramsay,3 and other eminent men.
I have now to offer a proof of the sliding of the ice exactly complementary to the above. Suppose a glacier to be a plastic mass, which did not slide, and suppose such a glacier to be turned upside down, so as to expose its under surface; that surface would bear the impression of its bed, exactly as melted wax bears the impression of a seal. The protuberant rocks would make fallows of their own shape in the ice, and the depressions of the bed would be matched by protuberances of their own shape on the under surface of the glacier. But, suppose the mass to slide over its bed, these exact impressions would no longer exist; the protuberances of the bed would then form longitudinal furrows, while the depressions of the bed would produce longitudinal ridges. From the former state of things we might infer that the bottom of the glacier is stationary, while from the latter we should certainly infer that the whole mass slides over its bed.
In descending from the summit of the Weisshorn on the 19th of August last I found, near the flanks of one of its glaciers, a portion of the ice completely roofing a hollow, over which it had been urged without being squeezed into it. A considerable area of the under surface of the glacier was thus exposed, and the ice of that surface was more finely fluted than ever I have observed rocks to be. Had the tool of a cabinetmaker passed over it, nothing more regular and beautiful could have been executed. Furrows and ridges ran side by side in the direction of the motion, and the deeper and larger ones were chased by finer lines, produced by the smaller and sharper asperities of the bed. The ice was perfectly unweathered, and the white dust of the rocks over which it had slidden, and which it had abraded in its passage, still clung to it. The fact of sliding has been hitherto inferred from the action of the glacier upon the rocks; the above observation leads to the same inference from the action of the rocks upon the glacier. As stated at the outset, it is the complementary proof that the glacier moves bodily over its bed.
Your obedient servant, | John Tyndall.
Royal Institution, Oct. 21
RI MS JT/6/5/1
J. Tyndall, ‘An Alpine observation’, The Times, (22 October 1861), p. 10.
Venetz: Ignace Venetz (1788–1859), Swiss engineer whose 1833 work Mémoire sur les Variations de la temperature dans les Alpes de la Suisse suggested that Europe used to be covered by glaciers.
Buckland: William Buckland (1784–1856), geologist who served as Reader in Mineralogy at Corpus Christi College, Oxford, and would go on to become Dean of Westminster. Convinced by Agassiz’s glaciation theory, he served as the proponent of that theory in England (ODNB).
Ramsay: Andrew Crombie Ramsay (1814–1891), Professor of Geology, Royal School of Mines and later Director General of the Geological Survey (ODNB).
Please cite as “Tyndall1816,” in Ɛpsilon: The John Tyndall Collection accessed on