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340 would indicate from the elastic modulus, but from which it was found to fall short by -ths or -ths. Subsequent determinations of the actual transit velocities in nature, by Nöggerath, by Schmidt, and here by myself, have proved the correctness of those first experimentally obtained, transit velocities, and subsequent researches will, I rest assured, equally confirm the generally low velocity of earthquake shock itself, now for the first time announced. It must not be understood, however, that the velocity of shock in all parts of the world, and from every earthquake, is limited to about 12 or 13 feet per second. And hence an interesting question arises, of what is the greatest possible velocity of shock that has ever occurred, or may occur.

We have, curiously enough, one fact recorded on no less authority than that of Humboldt, which enables us to answer this in part.

In the great earthquake of Riobamba, 4th February, 1797, "The explosive movement," he says (Humboldt, Voy. tom. i. p. 317, and Cosmos), "was such, as is produced by the firing of a mine, and the vertical action from below upwards, was most conspicuously displayed near the town of Riobamba, which was totally destroyed, when the bodies of many of the inhabitants were thrown upon the hill of La Culla, which rises to the height of several hundred feet at the other side of the Lican torrent." The actual range of vertical projection of these bodies, has been estimated at 100 feet. The velocity due to this height of projection is,

and this is probably the greatest velocity of shock recorded, or perhaps at present possible upon our earth; it is nearly