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Page:Popular Science Monthly Volume 70.djvu/403

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THE JAMAICA EARTHQUAKE

PSM V70 D403 Closer view of the submergence at port royal.png

Fig. 15. Nearer View of Submergence at Port Royal, looking south. Most of the area now covered by water in the photograph was formerly land.

or so of the cable had to be abandoned. The preliminary tremors were heard before being felt and probably were slower than sound-waves. With the increase of speed that comes with the augmentation of intensity of earthquakes, it is probable that the rate of the major vibrations was about ten thousand feet per second.

As has been previously stated the shock was a double one; the first climax apparently came from the west, while the second one, less disputive and more undulating in its character, apparently came more from the southward of Kingston. These two directions of vibration resulted in an almost universal gyratory movement of columns, statues, piers, sections of brick chimneys, and even of buildings, in a counterclockwise (Fig. 10) fashion.

Geologically, earthquakes often are not very important. In the case of the earthquake at Jamaica, however, there apparently was a

PSM V70 D403 Twisted rails and tilted buildings at the victoria battery in port royal.png

Fig. 10. Twisting of Rails and Tilting of Buildings in Victoria Battery, Port Royal, by Subsidence.