More particularly, safety devices which, while protecting against one agent of destruction, attract magnet-like another and worse. Such as the armored cable within the walls of a wooden house. It protects the electrical conductors within it against accidental external shorts; but, inadequately grounded, it may attract and upon occasion has attracted the stupendous force of lightning. Then, steel armor exploding into incandescence inside walls and ceilings, that house’s existence thereafter is to be measured in minutes.

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