What does a pen have to do to record on paper the vibrations（ 振动） generated（产生） by an earthquake? An earthquake comes like a thief in the night without warning. It was necessary, therefore, to invent instruments that neither slumbered（睡眠） nor slept. Some devices were quite simple. One, for instance（实例）, consisted of rods（杆） of various lengths and thicknesses（厚(度)） which would stand up on end like nine pins. When a shock（ 震动） came, it shook the rigid table upon which they stood（站立）.

  If it were gentle, only the more unstable（ 不稳定的） rods（杆） fell. If it were severe（严格的）, they all fell. Thus（如此） the rods（杆）, by falling and by the direction in which they fell, recorded for the slumbering scientist the strength of a shock that was too weak to awaken（唤醒） him and the direction from which it came. But instruments far more delicate（纤细的） than that were needed if any really serious advance（进展） was to be made. The ideal（理想） to be aimed at was to devise（设计） an instrument that could record with a pen on paper the movements of the ground or of the table as the quake passed by. While I write my pen moves, but the paper keeps still.

  With practice, no doubt, I could in time learn to write by holding the pen still while the paper moved. That sounds a silly suggestion, but that was precisely（正好） the idea adopted（采用） in some of the early instruments seismometers for recording earthquake waves.