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Show LUCKY FOB THE BIG CITIES. Probably no person unaccustomed to such an experience ever stood on the roof of a twenty-story building", when a great wind was blowing, without a tremor of tha nerves, and at least an Imaginary sense of swaying in tha huge structure beneath his feet. There is such a swaying, and It has been measured meas-ured with great exactness. But it. turns out. to ba far less than is Imagined, says Garrett P. Serviss In Success. CarefOl observations to determine the amount of oscillation .of tall buildings in a high wind were made In Chicago a few years ago, during a tempest in which tha velocity of the wind reached eighty miles an hour. Tha Monadnock building, 200 feet In height, and unprotected unpro-tected In Its upper part by neighboring edifices, swayed only one-quarter to one-half an Inch from tha perpendicular! perpendicu-lar! . j. Bat it should not be Inferred from this that no special effort Is needed to I secure a lofty building from the effects of the wind. On the contrary tha slight decree of oscillation mentioned above was due to the fact that the engineer-architect engineer-architect had calculated beforehand the atmospheric forces that his building would have to resist, and had provided ayalnst them by means of a system of "wind bracing." This is one of the niceties in the mod- , em art and science of building. Experiments Ex-periments and mathematical caicula- m tlons, of which the general public can ( have little idea, have determined 'the t pressure exerted against lofty struc- t tures by winds of various velocities, j and also the best methods of enabling . the bulldlnrs to withstand these pres- sures. When a building 200 feet tall sways only a quarter of an inch out of j the perpendicular. In tha face of a hur- ; rlcane pushing against It with a force -of thirty pounds on every square foot j of Its surface, that fact is a testimonial j to the success of scientific "wind brae- lng." People who sit secure and indlf- ; ferent in their offices, 200 or 200 feet above tha pavement, and hear the wind ; howl and hurl its blasts about the steel ; cage that incloses them, think little of 1 the mathematics on which their safety Is based: but if that mathematics were not the surest product af the human mind, they might find themselves at the bottom of a tangled wreck. "What Is wind bracing, then?" It may be asked. It is a system of steel connections which. In the body of a UU building, serve a purpose similar to that of the Interlacing muscles and tendons which bind -together the bones of the human skeleton, and enable It to act all together, to-gether, as a unit. In resisting forces tending to upset or crush it. In a scientifically sci-entifically constructed building the force of the wind pushing against its upper portion arouses a resistance which is transmitted downward from story to story, and distributed on all sides from member to member of the steel skeleton, until It is felt at the foundations, and thus the strength and weight of the lower portion of the building, lying in the shelter of the surrounding sur-rounding edifices, out of the reach of the wind above, are brought Into play ( for the common defense, very much as , the effects of a push against a man's -shoulder are distributed throughout his . muscular system, down to his feet, and are thus resisted by his whole body. |