Evening star. [volume] (Washington, D.C.) 1854-1972, 1894-08-04
NM


= .|FJlf were trying to be
-~ over-original In your
~[--I - hyperbole He would
wonder why you
i ~ didn't say It's hot
enough to melt the tail off a brass monkey"
or, Its hot enough to fry eggs" If you
are just little pinched for cash when he
guys you for being far fetched" make 1t
q wager and take him to the office Of
Architect Clark, or show him the plummet
line which hangs from the top to the bot
tom of our giant obelisk.
That these immense structures move. and.
IN fact, that all stone or metal buildings
are constantly changing their positions
under different temperatures, Is a fact not
generally realized. Washington is the best
place on eartl. to study the effects of sun
light on massive buildings, for here the rays
of Sol are not impeded by closely adjacent
edihces. as they are in most of our large
cities. The great dome of the Capitol 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
when it Is known that it's mammoth mass
really sways back to the south and west,
as II striving to find refuge from the heat.
Architect Clark, who has had the custody
of the Capitol for nearly forty years, has
experimented by means of a pluminet line,
and has. surprised even the prominent en-
Glneers of the army by observing that on a
hot day the expansion of the iron IS sufii-
GENTLY great TO thrust the sunny side of the
dome back. The top feather in the head
dress OF the statue of Freedom describes an
irregular eiiipse, whose major axis on
very warm day Is a half of a foot, and
the hotter the day the greater the axis
The giant plinth base Of the DOME resting
on the roof of the old sandstone building
measures $50 1-2 feet on side. The great
Fafasr at ~ t. sp-
while the whole iron structure is 21S feet
high. from the old Capitofs roof to the base
OF the statue. The cast iron covering this
Surface is made in thin plates Offering a
good conductor for the heat, which swells
the very bolts and beams of the inside, be-
fore the sun has made its circuit.
In Summer Clothes.
If the dome were made IN one mass. and
not composed of separate plates fitted with
Joints fixed loosely to allow expansion, as
IT Is, the motion in the sunlight would be
several feet, while IL the surface were
painted black, which absorbs the heat, the
huge thirnble would go over still more
White raiment reflects the suns rays from
great buildings as well as an array of duck
or of pure linen, throws the units of heat
from the human habitation. The contrac-
ton caused by cold atmosphere in winter
Is uniform on all sides OF the dome caus-
Ing no strain to any particular part, so
Uncle Sam has done we'll to clothe his
buildings In summer colOrs, II IL Is better
Tor them to be too cold than too hot The
southern side of the dome suffers most
from the heat, being exposed longer to the
sCn. which passes south of the zenith while
on its journey from the east to the west.
II the metal were exposed to a constant
heating, the result of the continuation of
such expansion as that received on these
torrid days might prove disastrous, but as
II Is. little IL any, permanent injury is DONE
since the iron returns regularly to its nor
NAL position. The only damage which this
gradual contraction and expansion may ul-
omateiy cause Is the weakening of the
connection between the metal base and the
roof of the sandstone building; but up to
this time no evidence of a breakage has ap-
peared The sandstone Is of the poorest
quality. which may become sufficiently
crumbled In the future to allow slight sep
aration. The castings of the iron plinth are
thicker than the upper metal work and are
poorer conductors. The sandstone also ex-
pands with the iron more than would
possessed by the material.
But what seems more astounding Is the
TACT that marble also is changed In vol
TINE so perceptibly by the sunlight that
monument sways back and forth in the
sun on a hot day. The movement of this
edifice is generally either north, SOUTH east
er west. rather than in Il direction through
sides. The outer surface being of hard
marble. the expansion Is much greater than
It would have been had granite been used
On hot summer day the sharp aluminium
apex which crowns the obelisk points I'D
ward from a position at least four inches
north OF It's normal, but always returns
TO its proper position in the cool of the
night. From the extreme top of the monu-
ment. inside, long pipe line runs perpen-
dicularly TO the bottom. leading to a small
closet back Of the elevator.
Recording the Movement.
This contains a long pendulum, whose
bob hangs In a vessel of mercury, which
prevents its oscillation. Two stationary
transits, with highly magnifying lenses. are
focused directly upon the suspended wire,
and through these each CULVER of the monu-
ment is detected. being magnified on a fine
ecale graduated 20 thousardths of inches.
Every morning at 10 o'clock the statement
Of this plummet line Is taken. This read
Ing is reported each day to the War De-
partment, and now that all hands are sat
khed that the monument Is not settling
rreSularly. the daily observations have be-
come merely part Of the routine. But by
means of this instrument 1t has lately oc-
CURED to the engineers to study the effects
CT hot weather upon the marble. Examina-
ton was made In the heat of the day. after
the sun had pierced through the particles
Of the southern face, and Ii was found that
the obelisk. Ike the great come across the
mall. had expanded. The whole shaft had
moved, and Its apex had left the normal
If II were made of one solid piece of stone
like the small obelisks Of the east the daily
deviation might be several feet and a con-
slant heat might topple 1t to the ground
But the monument. like the DOME Is elias
tic. When the night cools II, IL returns to
Its proper position. and records show that
It has ever behaved thus. Although the
greater weight of Its mass has pressed the
ground for many decades, 1t has settled
only very slight fraction of an inch in one
corner. This seems extraordinary when IL
10 realized that Its weight of ST. 100 tons
rests on a foundation only 128 LIZ feet
bquare and IS feet deep from a height al
most fifteen times that Of the depth The
whole rests only the sandy bank of the
Potomac, with the enormous pressure of
fve tons per square foot In the winter fts
movement has been as much as two inches
when sti1 gale has beaten IN against II
broa1sides. In fact. each gentle zephyr. as
well as each pencil OF light. moves it. pro-
port'onately. TO one side or the other but
calm never fails TO put II back in it's
place. any more than does the cool of night
On August 81. 1885, the earthquake which
gave Washington a shaking. did the monu-
ment no permanent injury although II
caused considerable motion in the shaft
especially IN the upper portions. After ex-