Devils Lake inter-ocean., 1913-05-23
HEAT o. TIL sun |
Old Sol Has a Strong Pull at the
Capitol In Washington. /.
SWAPS THE MAMMOTH DOME.

SWAPS The MAMMOTH DOME.
On q Hot, Day His Torrid Rays VIII
II, Drag the Massive Iron Structure
y Way Out Of Piumb-Turns the Sams.
Trick With Washington Il M onument ss
y Not many people have any idea as to
the enormous amount of heat that the
sun sends off into space. The earth
gets only very small portion of it.
The head of pin placed twenty feet
away from an electric light gets
In proportion to the light on the sur
rounding walls of room about what
the earth gets of the suns light and
heat radiated into space. Yet that por-
ton the earth does get is great enough
to cause great structures to move. As
In fact, all stone or metal buildings
are constantly changing their positions
under the hot rays of the sun. The
great dome of the capitol building at
Washington is the largest surface Of
cast iron In the world. and the effect Of
the continuous heat of a hot summer
day can best be appreciated, says Har-r
per's Weekly, when it is known that
this mammoth mass really sways back
and forth under the scorching rays un-
til the top feather in the cap of the
statue of Freedom describes an ellipse
the diameter of which on hot day
varies from four to eight inches. ii.
The giant plinth base Of the dome,
resting on the roof Of the old sand
stone building, measures 1856 feet on a
side. The greatest diameter, of the
round dome is l25 feet, while the
whole iron structure is 21S feet high
from the old capitol's roof to the base
Of Freedom on the apex. The cast iron
covering this surface is made in thin
sheets. offering a good conductor for
the heat. which swells even the bolts
and beams CT the inside before the sun
has made its circuit.
The southern side, of the dome suf-
fers most from the heat, being expos
ed longer. to athe sun. which passes
south of the zenith while on it's jour
my AloAA SAG Suol " luC west. IL llc
metal were exposed to a constant
heating; the. result. of the continuation
of such expansion as that received on
very hot days might prove disastrous,
but as it is little if any permanent in
jury is done. since the iron returns
regularly to its normal position as the
cool night comes on. ''ts
But what seems more remarkable is
the fact that marble is also changed in
volume so perceptibly by the sunlight
that the mammoth shaft of the WASH
ington monument sways back and
forth in the sun on a hot day. The
outer surface being of hard marble the
expansion is much greater, than it
would be had granite instead of mar
bic been used. On hot summer day
the sharp aluminium apex that crowns
the obelisk points to position atIeast.
four inches north Of normal, but al
ways returns to its proper position in
the cool Of the night. ",.
From the extreme top Of the monu-
ment inside long pipe line runs per
pendicularly to the bottom, leading 10
small closet behind the elevator.
This contains a long pendulum, whose
bob hangs in vessel Of mercury,
which prevents its oscillation Two
stationary transits with highly mag
nifying lenses are focused directly
upon the suspended wire, and through
these each quiver Of the monument is
detected, being magnihed on fine
scale graduated to thousandths Of an
inch. ~
Every morning at 10 o'clock state
ment Of this plummet line is taken
and reported to the war department.
and 1t was by this means that the ef-
feet which the SUMS rays have on the
huge white shaft was discovered. This
plumb bob. of course, was placed in
the monument for the purpose Of de-
tecting any settling 1t might undergo,
and, although the great weight Of it's
mass has pressed the ground for many
decades, It has settled only "a slight
fraction Of an inch in one corner. *; y
This seems extraordinary when it is
realized that it's weight Of 81, ,72O tons
rests on a foundation only 1861 feet
square and SO feet deep from a height
almost fifteen times that Of the depth.
The whole rests on3the sandy bank or
the Potomac river. with the enormous
pressure Of Ave tons to the square
foot I, Not only does the suns heat
sway the big obelisk. but at times,
when stif winter gale was blowing,
II has been reported as much as two
inches out Of plumb. :. G35 tS5s' NE <ss5 MI