A good idea of the old church clocks may be obtained from the picture
herewith. Tradition has followed it down as the “English Blacksmith’s
Clock.” It has the very earliest application of the pendulum. The
pendulum is less than 3 inches long and is hung on the verge, or pallet
axle, and beats 222 per minute. This clock may be safely put at 250
years old, and contains nothing invented since that date. Wheels are
cast brass and all teeth laboriously filed out by hand. Pinions are
solid with the axles, or “staffs,” and also filed out by hand. It is
put together, generally by mortise, tenon and cotter, but it has four
original screws all made by hand with the file. How did he thread the
holes for these screws? Probably made a tap by hand as he made the
screws. But the most remarkable feature is the fact that no lathe was
used in forming any part--all staffs, pinions and pivots being filed by
hand. This is simply extraordinary when it is pointed out that a little
dead center lathe is the simplest machine in the world, and he could
have made one in less than a day and saved himself weeks of hard labor.
It is probable that he had great skill in hand work and that learning
to use a lathe would have been a great and tedious effort for him. So
we have a complete striking clock made by a man so poor that he had
only his anvil, hammer and file. The weights are hung on cords as thick
as an ordinary lead-pencil and pass over pulleys having spikes set
around them to prevent the cords from slipping. The weights descend 7
feet in 12 hours, so they must be pulled up--not wound up--twice a day.
The single hour hand is a work of art and is cut through like lace.
Public clocks may still be seen in Europe with only one hand. Many have
been puzzled by finding that old, rudely made clocks often have fine
dials, but this is not remarkable when we state that art and engraving
had reached a high level before the days of clocks.
[Illustration: THE LARGEST CLOCK IN THE WORLD
Courtesy of Colgate and Company.
THE HANDS OF THE LARGEST CLOCK IN THE WORLD--ON THE ROOF OF THE COLGATE
FACTORY.
This big clock faces the giant office buildings of down-town New York.
Its dial is 38 feet in diameter and can be read easily at a distance
of three miles, so that passengers on the incoming liners pick out the
clock as one of their first sights of New York.
The next largest clock (on the Metropolitan Tower) is 26¹⁄₂ feet in
diameter; the Westminster clock of London, 22¹⁄₂ feet.
The great clock weighs approximately 6 tons. The minute hand, 20 feet
long, travels at its point 23 inches every minute; more than one-half
mile each day.
The bed of this clock is 4 feet in length, the wheels and gears being
made of bronze and pinions of hardened steel. The time train occupies
about one-third of the bedplate, and has a main time wheel measuring
18¹⁄₃ inches in diameter. This train is equipped with Dennison’s double
three-legged gravity escapement, which was invented by Sir Edmund
Becket, chiefly for use on the famous Westminster clock, installed
in the Parliament Buildings, in London, England. The use of this
escapement is most advantageous for a gigantic clock of this kind as it
allows the impulse given the pendulum rod to be always constant, and
therefore does not permit any change of power or driving force of the
clock to affect its time-keeping qualities.
It requires about 600 pounds of cast-iron to propel this time train,
and the clock is arranged to run eight days without winding. The
gravity arms of the escapement are fastened at a point very near the
suspension spring, and the arms are fitted with bronze roller beat pins.
The dial contains 1134 square feet, or about one thirty-fifth of an
acre. The numerals consist of heavy black strokes, 5 feet 6 inches
long and 30 inches wide at the outer end, tapering to a point at the
inner end. The circumference of the dial is approximately 120 feet. The
distance from center to center of numerals is 10 feet, and the minute
spaces are 2 feet.
The background on dial is painted white, and in the daytime the black
numerals show up distinctly. At night the numerals, or hour marks,
are designated by a row of incandescent bulbs placed in a trough 5
inches wide and 5 inches deep. The hands at night are outlined with
incandescent electric lights, there being 27 lamps on the hour hand and
42 lamps on the minute hand.]
[Illustration: THE MACHINERY WHICH RUNS A BIG CLOCK]
This picture shows the machinery necessary to operate a large modern
tower clock.
The mechanism is held in place and confined entirely within a cast-iron
structure which is firmly bolted to the floor. The wheels are composed
of bronze, the pinions of steel (hardened) and the gears are machine
cut. At the front of the clock is a small dial which enables one to
tell exactly the position of the hands on the outside dials, and there
is also a second hand to permit of very close regulation and adjustment.
Three ways are provided for the regulation. First by a knurled screw
at the top of bed frame. Second by a revolving disc at the bottom of
the pendulum ball. Very often by either of these two methods it is
impossible to bring the clock to fractional seconds, and in order to
permit of a nicety of adjustment there is a cup fitted at the top of
the ball so that by inserting or taking out lead pellets, the rating
can be brought to absolute time.
[Illustration: THE CLOCK IN INDEPENDENCE HALL