The forms of water in clouds & rivers, ice & glaciers / by John Tyndall ... with thirty-five illustrations drawn and engraved under the direction of the author.

  • Tyndall, John, 1820-1893.
Date:
1873
Catalogue details

Licence: Public Domain Mark

Credit: The forms of water in clouds & rivers, ice & glaciers / by John Tyndall ... with thirty-five illustrations drawn and engraved under the direction of the author. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    481. Turn into any well-arranged museum—for example, into tlie School of Mines in Jermyn Street, and observe the evidence there collected. Look particularly to the fossil trilobites taken from the slate rock. They are in some cases squeezed to one third of their primi- tive thickness. Numerous other specimens show in the most striking manner the flattening out of shells. 482. To the evidence adduced by Mr. Sharpe, Mr. Sorby added other powerful evidence, founded upon the microscopic examination of slate rock. Taking both into account, the conclusion is irresistible that such rocks have suffered enormous pressure at right angles to the planes of cleavage, exactly as the glacier has demonstrably suffered great pressure at right angles to its planes of lamination. 483. The association of pressure and cleavage is thus demonstrated; but the question arises, do they stand to each other in the relation of cause and effect? The only way of replying to this question is to combine artificially the conditions of nature, and see whether we cannot produce her results. 484. The substance of slate rocks was once a plastic mud, in which fossils were embedded. Let us imitate the action of pressure upon such mud’ by employing, instead of it, softened white wax. Placing a ball of the wax between two glass plates, wetted to prevent it from sticking, we apply pressure and flatten out the wax. 485. The flattened mass is at first too soft to cleave