EARTHQUAKES CAUSED BY CHILDREN.

Pelorus Guardian and Miners' Advocate., Volume 18, Issue 31, 16 April 1907, Page 2

EARTHQUAKES CAUSED BY CHILDREN.

j The wonderful force of vibration is recognised in all its powers by few architects and builders. It would amuse them if they were told that the most solidly built of their walls would be injured by the continuous scraping of a bow across the violin. 01' course, it would take years of playing to loosen niasonary and render iron brittle, but. there are facts on record which show that such a result has occurred. On a first-class battleship a man may feel the vibrations of a violin though,he may not be able to hear the music. It is the regularity of the vibrations which tells. The player is not affected by them, for he is a flexible object and can give way to motion.

Every one knows that a squad of soldiers or any body 0 f marching men break step in crossing a bridge, no matter what its size and strength may be, for none could withstand the vibrations of this concerted action. Even the tread of a dog may make a bridge shake because of the regularity of the vibration, so that on many of the big suspension bridges dogs are not allowed unless carried in the arms of their owners.

A good illustration of tho power of vibration can be found in the Greenwich Observatory. ]|, stands on tho top of a hill on whose slopes hundreds of children play on fine evenings. Their favorite game is to join hands at the top and dash headlong to the bottom, where they fall in a heap. This starts the vibration of tho hill to such an extent that the scientists of the observatory are unable to carry on their observations, which depend on the motionless state of a tray of mercury. The solid hill is in such a state of tremor Unit the vibrations continue till long past midnight, when the children who have caused it have been asleep for hours.