Evening star., 1898-12-20
PHILADELPHI,'s NEW CLOCK.
The Huge Afair Of the city Hall soon
to he started.
From the Philadelphia Press.

From the Philadelphia Press.
The great clock in the tower ~ city hall
is running, although this fact is not yet ap-
| parent to an outside observer The clock
will be kept In operation for month in
order TO test its accuracy. and Its hands
| will begin TO move at C o'clock on New Year
eve.
To most people the marvellous intricacy
| and the magnitude OF the big tImepicca
would prove a surprise 1t seems to be
| popular opinion that the clock is run by
| works located behind the dial and similar
| to those concealed in the interior OF an or
dinary mantel-shelf chronometer. The
| mechanism that controls the mighty hands
of the city clock is vastly different from
| common clock works.
The hands OF the clock are TO he moved
| by machinery. stationed more than one
| hundred feet below them The main mech
anism, or master clock" as II is called IS
| located in the seventh loor of the tower.
In one corner of the tower stands a huge
glass cabinet. which. with the addition of
flowers and plants. would make a good con-
SeTN atory. This cabinet is ten feet high,
fifteen feet I'm length. and. although seem
ing to rest on the floor. Is in reality sus-
pended by iron beams prutruding from the
tower walls. The cabinet is almost as
carefully made as the clock itself. The
framework is composed of iron and soft
pine the whole being overlaid with copper.
A mahogany door leads into the cabinet.
and when this is closed the cabinet is alb
sOlutely air-tight and dust-proof
Standing inside thc cabinet on perfectly
level arble floor are two clocks four feet
in height, and inclosed in cases Of glass
and ebony. One Of these clocks is the vital
part of the elaborate system. the other
clock serves as an auxiliary. The interior
of the cabinet is kept at one temperature
by means Of thermostat that automau-
heat in an electric coil
The master clock was made in Glasheut-
ter. SaNony, and required two years I'm st.
manufacture. 1t is so arranged that knob
attached to the long pendulum opens a
valve at every half minute The opening
of the valve permits a current pf com
pressed air to flow through a small brass
pipe to the central movemtn nj, which is one
hundred feet above in the chamber OF the
tower behind the clock faces. Whenever
the valve is opened the compressed air
pushes forward or backward a delicate dia-
phragm which by its movement causes
toothed wheel to revolVe through a dctin-
ite arc. To this toothed wheel is attached
by a universal joint a long brass rod that
runs to the axis of the hands IN the big
clock and turns them. 1t Will be seen.
therefore, that the hands Of the clock move
at intervals of thirty seconds. the minute
hand describing a complete circle by a Sc
ries of one hundred and twenty hort ad-
vaLceS For each of the four dials there
is a central movement. all four movements
being operated simultaneously by the COM
side the cabinet. behind the master clock"
In addition to this careful and complex
arrangement are the three electric pumps
that work automatically and keep the air
pressure at ten pounds. To protect against
accidents two other pumps have been
placed in an entirely different part OF the
city hail. and in case the air pressure
should fall through accident below seven
pounds the two distant pumps would take
up the work.
The dials are Illuminated at night by five
hundred and fifty-tWo lncandescent lights,
and in this connection there is another in
teresting automatic arrangement that turns
on the lights whenever darkness comes. In
side the cabinet. behind the master clock.
is a telephons connection direct with WASH
fngton, and through it the ticking Of the
astronomical clock i'm the government OBJ
servatory can be heard BY this means any
error in the reading Of the city han CLOCK
can he detected and corrected.
Each hour hand is thirteen feet threo
inches and each minute hand IL sixteen feet
five inches in length. Each hand weighs
four hundred poun Is. and Is made OF brass.
The entire clock cost the city S2H"'l.