The Savannah morning news., 1901-11-10

! struct an iron shaft or the quarryman
! able TO erect a stone shaft in one solid
| piece mile high, the top of that shaft
would nod its head slightly at the sun
just as surely as the more flexible sun
flower does now each day. For all tall
/ structures move, skyscrapers, church
| steeples. monument and tall towers
| bend over or follow the sun around in
a circle each day. All bridges slide
/ forward and back on hot and cold
/ days The Brooklyn bridge has indeed
/ a buckling plate in its center, which
! is intended to take up the sliding mo-
! ton that constantly goes on in the
! structure. This movement of bridges is
| somewhat on the principle of the
] creeping of railway tracks, which con-
! tract in cold and expand in hot wealth
| err, sometimes to the extent of four
hundrd and twenty millimeters to the
rail. There is on the banks of the Mis-
souri, river vast quantities OF sand
which are constantly in motion. OF
course, glaciers move, and there is
mountain in France which has NOV
ed it's position perceptibly in a centu-
ry. st. Paups Cathedral in London not
only has a tower that moves back and
| forth, but the building itself is thought
to be sliding slowly into the Thames.
The Washington monument on the
bank of the Potomac is so noted for
nodding its head at the sun that the
engineers
| the structure to show just how much
it may go out of plumb. The monu-
ment of course, is hollow, and 144 feet
up the inside in one of the corners
extends a wire, hung from beam.
| On the end of this wire hangs 20
pound plumb made of brass. 1t
| just clears the floor. On a platform
nearby is affixed a spyglass the OBJ
| jective of which has a vertical line
| scratched upon 1t. The glass is affixed
| to graduated scale and may be NOV
| ed forward and back by means of
| thumb screw. Under normal conditions
| the spyglass is adjusted so that If you
loook through it the long wire with
| the plumb-bo on the end will be di
rectly opposite the vertical line
scratched on the objective. On hot
| days the top of the monument leans
over, and, of course. the plumb-bob
| swings over with it like a pendulum.
BY adjusting the glass until the two
| lines are directly opposite again the
| graduated scale Immediately shows
| how great movement has taken place.
1t is calculated that this leaning has
been at times as great as four inches.
The dome of the Capitol building in
| Washington has an elliptical movement
| and an experiment was tried to show
| it's scope. A wire was hung from the
middle of the dome inside the build
x.
rotunda, and on the lower end Of the
wire was hung a plumb-bob similar to
| the one in the Washington monument.
| But in the lower point of the weight
| was inserted a lead pencil. The point
of the pencil just touched the floor.
A large sheet of paper was spread
upon the floor. Every day as the
| dome moved it dragged the pencil
over the paper. The mark made was
| in the form of an. ellipse six inches
| long. The dome would start moving in
| the morning as soon as the rays of the
sun began to act upon it, and slowly,
| as the day advanced, the pencil would
| be dragged in a curve across the paper
until shutdown, when a reaction would
take place, and the pencil would move
back again to it's starting point. But
| IL would not go back over its own PEN
| Ciled track, for the cool air of night
would cause the dome to contract as
| much on the one side as the sun had
made it expand on the other, and so
| the pencil would form the other half
| of the ellipse, getting back to the start
ing point already to start out again
| by sunrise. One of the guides in the
| building says he was able within GER
| tain limits to tell the time of day by
| the position of the pencil on the paper,
and it is easy to imagine a clock, the
| face of which would be the ellipse with
| the figures drawn in their places and
| the hand of which would be the plumb
| bob hanging on the wire and pointing
| to the time of day.
| The Philadelphia City Hall, which is
| higher than the Washington Monument,
| leans a trife every day, and the Eiffel
| Tower, in Paris insisted on moving in
| curves and leaning so much that it
once got upon the nerves of the ex-
| citable Partisan public They thought
iph "a nj Of he
| French army, who made the tests of
| the towers movements, found that the
| expansion and contraction of the iron
| in the tower causes it to describe a
| torsion movement between sunrise and
| sunset, which traverses a curve of ten
centimeters OF course. a backward
movement equally as great occurs dur
| ing the night.
So it is with all the other domes and
| towers and statues and bridges and
even with the tall office buildings No
| experiments have been made with sky
| scrapers as yet, but they move just as
| surely as do the other structures The
movement of St. Pauls bodily towards
| the Thames is due to the subsistence of
the sub-soil on which the cathedral is
built. Even in the days of Wren, who
| took every precaution, it was noticed
| that the great weight of the building
had disturbed the ground a little. One
hundred years ago the building was
braced with iron ties. Yet the drain
age that has taken place and the tap
pings of the underground railroad have
weakened the conditions of the neigh
boring ground. The south transept has
begun to slide southwark, and one
| great wall nearly ten feet thick and
one hundred and thirty feet wide has
opened and started to slide towards the
river. In this, of course, there is dam
ger, but there is no danger in the move
ments of towers, for the expansion due
to heat and the contraction due to cold
is very natural condition and one
that must always be taken into account
by the architects. No great tower
could possibly be absolutely rigid
WITH THE NARROWED Beers.