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Page:Popular Science Monthly Volume 70.djvu/398

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394
POPULAR SCIENCE MONTHLY


PSM V70 D398 Gables destroyed by the shock.png

Fig. 8, a. East and West Gable Ends destroyed by Shock.

From the data available, the dependence of earthquakes in intensity upon topography is well emphasized. Loosely compacted fringing and alluvial plains extended the intensity farther than the more compact and elastic mountain regions. Not only do these less elastic plains give a greater amplitude to the waves and cause greater destruction, but apparently the earth-waves are affected by plains indented in hills as sea-waves change their direction in entering the arm of a bay. The arrows (Fig. 1, a) indicate generally the direction of the wave motion. In the middle of the Hope River Valley at Mona Plantation an observer noticed the motion pass him and then saw the landslide occur at the mouth of the river to the southward. As the wave passed over the cane-fields, a motion was observed similar to that produced in a field of grain by the wind. The direction here was at right angles to the path of the wave-motion only five miles away at Kingston, situated on the western slopes of Long Mountain. The motion approached the island from the southwest, changing on the land its direction and intensity with the change in the nature of the material through which it passed. In the lower part of the city of Kingston the path of the movement was well marked by the overthrowing of walls, piers, statues, monuments, large chimneys and a similar movement toward the east of even large marble slabs covering graves (Figs. 3-9). Northward from the city the motion appeared to come more from the south, and the northern walls showed the greatest damage; and westward, the path of motion appeared to swing so that it came from Kingston. The absence of any large buildings, away from the villages and cities, made the plotting of directions rather difficult, for the lightly-built mud-wattled huts were not affected by the shock and tests by hearing are very unreliable. But there was a general diminution in intensity away from Kingston;