Читать книгу The Romance of Modern Geology. Describing in simple but exact language the making of the earth with some account of prehistoric animal life онлайн

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It would seem, therefore, that either these shocks or breakages in the earth's crust, or the earth's interior, must be very great indeed, or else that the earth must be composed of rather shaky materials. Well, perhaps both these suppositions are true. We spoke just now of the instruments which seismologists use to record earthquakes. They are known as "seismometers," and a great many of them are used in Japan and on the Californian or Pacific coast of America. Now it is perhaps scarcely necessary to say here (when we recollect how many cyclones and anticyclones England receives from the Atlantic) that a storm or rainy weather is usually heralded or accompanied by a fall in the barometer, or a depression. Now when there is a depression in the barometer that means that the weight of air above the barometer is less than it was before, though it is not so great a difference that human beings could tell it, unless it were accompanied by other signs. But the earth can tell it, and the mere fall of the barometer, owing to changes of the air, will make the earth tremble or quiver slightly, as if it were a jelly. We cannot perceive it; but the delicate seismometers can; and when a storm is coming to Japan or to California from the Pacific, the instruments show that the earth feels the passage of it. The comparison of the earth to a jelly—a very stiff jelly—is on the whole a useful one.