Idaho County free press. [volume] (Grangeville, Idaho Territory) 1886-current, 1912-12-26
HEAT OF THE sun
Old Sol Has a Strong Pull at the
capito! In Washington.
SWAPS THE MAMMOTH DOME.

Drag the Massive Iron Structure
Way Out Of Piumb-Turns Tie Same
Trick With Washington Monument.
Not many people have any idea as to
the enormous amount Of heat that the
sun sends OF into space. The earth
gets only very small portion Of 1t.
The head Of a pin placed twenty feet
away from an electric light gets
In proportion to the light on the sur
rounding walls of q room about what
the earth gets OF the suns light and
heat radiated into space. Yet that pOr-
ton the earth does get Ia great enough
to cause great structures to move.
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 ia the largest surface Of
cast iron In the world. and the effect Of
the continuous heat of a hot summer
day can best he appreciated. says Har-
per's Weekly. when 1t II known that
this mammoth mass really sways back
and forth under the sc0rching rays un-
til the top feather In the cap Of the
statue Of Freedom describes an ellipse
the diameter Of which on q hot day
varies from four to eight inches.
The giant piinth base Of the dome,
resting on the roof Of the old sand
stone building. measures 1856 feet on
side. The greatest diameter Of the
round dome h l26 feet. while the
whole iron structure II 218 feet high
from the old capitOls roof to the base
Of Freedom on the apex. The cast iron
covering this surface 10 made In thin
sheets. Offering a good conductor for
the heat which swells even the bolts
and beams Ut the inside before the sun
has made IT'D circuit
The southern aide Of the dome suf-
fers most from the heat. being expos
ed longer to the sun, which passes
south Of the zenith while on its Jour-
ney from the east to the west II the
metal were exposed to q constant
heating the result Of the continuation
Of such expansion a that received on
very hot days might prove disastrous.
but as 1t Is little II any permanent in.
jury IL done. since the iron returns
regularly to its normal position as the
cool night comes on.
But what seems more remark BILE 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.
BILE been used. On hot summer day
the sharp aluminium apex that crowns
the obelisk points to a position at least
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 to
small closet behind the elevator.
This contains 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 culver OF the monument is
detected. being magnified on a fine
scale graduated to tho,isandths of an
inch
Every morning at 10 O'Clock a state
mcnt Of this plummet line is taken
and reported to the war department
and II was by this means that the eff
feet which the suns 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 II might undergo,
and. although the great weight of it's
mass has pressed the ground for many
decades. 1t has settled only slight
fraction OF an inch in one corner
This seems extraordinary when It Ia
realized that its weight OF 81. 100 tons
rests on founda ton only 1851 feet
square and rs feet deep from height
almost fifteen times that of the depth
The whole rests on the sandy bank of
the Potomac river. with the enormous
pressure of five tons to the square
foot. Not only does the suns heat |
sway the big obelisk but at times.
when stiff winter gale was blowing,
t has been reported as much as two
inches out of plumb.