Virginia citizen. (Irvington, Va.) 1891-1921, 1908-01-31
THE WIND ALoFT.
Towering skyserapers Have to Stand a
Lot of Blowinu,

Towering Skyscrapers Have to Stand a
Lot of Blowing.
The wind velocity in the vicinity of
New York is not, on the average the
year round, extraordinary, but at times
IL blows at the rate of fifty and sixty
miles an hour. Then signs GO sc,Irry-
ing MP Broadway, umbrellas turn in
side out. and the wearers OF skirts
struggle frantically TO hoM together
their various articles OF clothing. The
man on the top of Il skyscuper Is like
a sailor sent aloft in storm 20 furl
sails. He clings 10y tooth and nail to
whatever support he can find and gets
down again, if he can, with more alac.
rity than lie went up. This wind We.
locity-not i'm its average. but at its
maXimum-is an important mathemat.
zeal problem with the engineer When
he runs building twenty TO forty
stories high. The wind pressure on a
tall building must he reckoned very
carefully. 4 structure five or six hun
dred feet in the mir must be braced to
Withstand Il wind pressure of some
thing like thirty pounds TO the square
foot. With tower sixN-five feet
square and several hundred feet above
the top OF the main building there Is
wind pressure ut certain seasons or
the year sufficient to drive n dozen
ocean steamers half across the ocean
IL IL could be harnessed and converted
into available horscpower. The re-
sistancc to this wind pressure must hs
secured by angle braces every second
or third story and the whole calculated
out by mathematical formulas.
II there is any doubt In the mind OF
the skeptical about the force of the
wind ut great attitudes, he should
drop plumb line from the top OF the
structure to the bottom Of some In.
closed court on a windy day. The line
would then be found to yibrate and
swing very much like the pendulum Of
a clock. A recent test OF the vibration
or tall building In a heavy wind was
thus made, and It was found that tho
line swung back and forth through an
arc OF nearly two degrees. Nature has
supplied us with something that corre-
spends TO 4 plumb line Our brains
appear TO float in liquid when stand
ing on vibrating tower, and the dizzy
sensation communicated to us is not
all fancy. The rocking OF a tower five
or six hundred feet in the air is not
very different from that OF n ship in q
sea. There are cases OF "seasick-
ness" among the cliff dwellers of Man
haitian, and they have to get accus-
toned to their high attitudes before
they are immune
If the wind pressure should at any
time reach the maximum stress al
lower for the Singer building, it would
represent over its whole surface e.
force equal to 12S,000 foot tons. AS the
total weight of the tower IS only %, 900
tons, Ii would be possible to overturn
this portion of the building, or, rather,
lift 1t up from its foundations. should
the wind blow at sach a velocity as to
exert an even pressure Of thirty pounds
per square foot. To avoid any such
contingency each heavy iron coluran fl
anchored to the foundation caissons
some sixty feet below the surface OF
the ground. The margin OF safety thus
obtained Is sufficient to withstand any
OF the summer wind squalls or tan
ends OF West Indian hurricanes which
sweep across Manhattan. - Harper's
Weekly.