Earthquakes And Other Earth Movements

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1903. Not illustrated. Excerpt: ... CHAPTER IL SEISMOMETRY. Nature of earthquake v... Read more

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1903. Not illustrated. Excerpt: ... CHAPTER IL SEISMOMETRY. Nature of earthquake vibrations--Many instruments called seismometers only seismoscopes--Eastern seismoscopcs, columns, projection seismometers--Vessels tilled with liquid--Palmieri's mercury tules--The ship seismoscope--The cacciatore--Pendulum instruments oE ICreil, Wagner, Ewing, and Gray--Bracket seismographs--West's parallel motion instrument--Gray's conical pendulums, rolling spheres, and cylinders--Verbeck's ball and plate seismograph--The prin iple of Perry and Ayrton--Vertical motion instruments--Record receivers--Time-recording apparatus--The Gray anc Milne seismograxjh. Before we discuss the nature of earthquake motion, the determination of which has been the aim of modern seismological investigation, the reader will naturally look for an account of the various instruments which have been employed for recording such disturbances. A description of the earthquake machines which have been used even in Japan would form a bulky volume. All that we can do, therefore, is to describe briefly the more prominent features of a few of the more important of these instruments. In order that the relative merits of these may be better understood, we may state generally that modern research has shown a typical earthquake to consist of a series of small tremors succeeded by a shock, or series of shocks, separated by more or less irregular vibrations of the ground. The vibrations are often both irregular in period and in amplitude, and they have a duration of from a few seconds to several minutes. We will illustrate the records of actual earthquakes in a future chapter, but in the meantime the idea that an earthquake consists of a single shock must be dismissed from the imagination. To construct an instrument which at the time of an earthquake sh... Less