Earth Tides

That the surface of the earth itself may be subject to tides like those of the ocean has long seemed probable,* but there has been no tidal gauge to measure these heavings accurately. At the University of Texas last fortnight a gravitimeter was announced which indicates a daily tidal movement of the solid earth at Austin amounting to two or three inches--larger than ever suspected.

The instrument, a refinement of the commercial gravitimeter used in locating oilfields, is a strong spring with a weight attached to its lower end. Any change in the pull of gravity changes the pull of the weight, shortens or lengthens the spring by an invisible amount. The instrument records fluctuations in gravity of one part in a billion.

At the University of Texas, Professor A. E. Lockenvitz is recording the local earth fluctuations. With gravitimeters installed at various points, he hopes to be able to predict earthquakes by noting prior increases in earth tides.

* The gravitational pull of the earth and the counterpull of the sun Si moon, which produce ocean tides, would logically also affect dry land.

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