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ECONOMIC GEOLOGY

Good ferro-concrete is so strong that the wall spaces are
not distorted and the building sways like a box. A census
of the damage wrought by the Tokyo Earthquake showed
that of 592 ferro-concrete buildings 78 per cent. were undamaged,
 and only 1-3 per cent. collapsed. The movement
causes the rectangular spaces in a steel framework to become
rhomboids, and if the partitions are of weak material, such
as lath and plaster, they are cracked and crushed in the
distorted frame.