Protecting Buildings from Earthquakes
Earthquakes are literally an every-day occurrence in Japan, and recent experiments by Professor Milne, of the Imperial College of Engineering, Tokio, show that the vibrations are chiefly horizontal, and generally in irregular ellipses, like the figure 8, in spirals, and many complicated forms. Even small areas have a variety of motions, in various directions, so that one part of a building is shaken in one direction while another part is shaken differently; spots of even small areas are free from vibration while others have a maximum motion, so that it is possible to select a spot for building where little or no shock is felt. Professor Milne has found that interposing small balls, say 1/4-inch shot, between properly formed plates, in the foundation of a large building, so that the whole could be moved a slight distance in any direction, caused the vibrations of the earth to be very slightly felt in the building. Also by digging deep trenches for the foundation walls, so that the latter did not come in contact with the surface of the earth, the vibration was very small. It is found necessary to either bind buildings, having ordinary foundations, very securely together, or to purposely allow different parts to vibrate independently. Chimneys, for instance, must not be connected to a building, as they are less liable to fall if standing alone.—Sabbath Recorder.