Science: Quake-Proof Clock

In old-fashioned earthquake recorders there was a heavy mass whose movements, amplified by a system of levers, were transmitted by means of a stylus to a recording drum. In modern instruments the stylus is replaced by a beam of light which makes its zigzag tracks on photosensitive paper. Actually it is not the heavy mass which moves, but everything else—earth, observatory, revolving drum —while the weight, which is freely suspended, remains still because of its inertia.

At the Carnegie Institution's seismograph station on Mt. Wilson in California, Dr. Hugo Benioff has built recorders which...