266
THE POPULAR SCIENCE MONTHLY
through intense heat in their process of manufacture. The internal framing, the skeleton, is of steel, thoroughly protected from fire by brick or hollow tile; the partitions and floors are also of tile; the elevators and stairways are enclosed and with automatically closing doors at every story so that each story is a unit by itself, virtually a separate
Fire's Ingress via the Window Route.
building. This is all-important. Fire's tendency is ever upward. Make it impossible for fire to travel from story to story and you have cut down your fire possibilities 90 per cent. And the same thing applies to each story. These should be so partitioned as to form as small
