Polynesian., 1858-06-26
The Chronometer,

The progress of the invention of the time-keep-
er was for ages almost imperceptibly slow.
First, there was the herdsman, watching the
sun by day, and the moon and stars by night
dividing the blue space into hand-breaths and
finger breadths, making use of his eve as a quad
rant to take attitudes Then the march Of the
shadow was graduated, and the dial presided in
garden and court yard. The hour glass of sand
or OF water was made to correspond to the divis-
ions on the dial plate, and good for nights and
cloudy days. Saturn, Chronos or Adam NAV have
carried one in his capacious sheepskn pocket. if
there was such thing as glass in his day, which
is doubtful.
The clepsydra, a sort of portable tide, was in
use long before the Christian era and so long as
two thousand years ago, Ctesibias of Alexandria
had added wheels to 1t, making it in fact water
clock, or clock going by water. 1t took about
a Thousand years more 70 invent the clock going
by weight and then it had no minute hand and
no pendulum to regulate its motion but balance
of two weights on lever, oscillating in a horizon
tai plane. The weights were movable on the
lever, and, by placing them nearer to or further
from the center of notion their vibration through
the arc determined by the pins or pallets which
played into the teeth of crown wheel was made
to be of such length as to give the hour-hand two
revolutions in twenty-fOur hours. Without the
balance, the weight, carrying the wheels with no
avoidable friction, would run down with an accel-
Grated velocity, OF course carrying the hand faster
and faster.
But tooth on one side of the crown-wheel, by
hitting pallet the arbor or axle of the balance
slowly sets Its ponderUus mass IN motion. and by
that motion carrying the pallet forward the tooth
escapes. The weight would now descend unob-
structed, but that tooth on the opposite side of
the crown wheel encounters another pallet on the
balance arbOr, is arrested by 1t, and has to destroy
all its motion and give it an impulse in the oppo-
site hpfO n md
Thus the descent Of the weight is cut up into
starts by the balance, and gravity acts constant
lv the same these starts must be equal. The
French monk, afterwards Pope Sylvester H., who
is said TO have set up the first clock of this sort
in Europe, was accused of having enjoyed diabOIi-
cal assistance; but he was more probably assisted
by the Saracens, with whom he had been acquain-
ted In Spain, and who were more advanced in me
chanics.
The balance of this primitive clock is substan-
tally the same as that of our present Watches aud
the crown-wheei escapement is hardly out of date.
But though the great mechanical principle of the
time-keeper-the division of a constant force into
equal portions was thus early developed, it requir-
ed some eight hundred years more to bring the ma
chine into the family circle and the pocket. 1t is
remarkable that the church tower clock had been
reduced to pocket size with acoiled spring instead
of weight as the moving power, and was actually
worn In the pocket, before the application of the
pendulum to the clock, or Of the balance spring to
the balance of the watch. These two great i'm
provements in theological mechanism were made
almost simultaneously, two hundred years ago ;and
history is inclined to divide the credit in both cas-
es. The spiral hair-sPring, by property pecul-
lar to itself, does the same for watch which the
pendulum does for a clock-that is with a proper
escapement, makes the vibrations the same in time
irrespective of the amount of force exerted by the
handspring. Before the hair spring and improved
eScapement were introduced, it was necessary that
the moving force should be constant and, as the
main spring pulled harder when fully wound up
than when partly So, it was made 10 act upon the
main driving wheel by means of chain coiled on
a snail or fusee, so that the Joss of force by the
uncOiling of the spring was compensated by the
chain acting further from the center
Though by the adoption of the hair-spriug and
improved escapement, this chain and fusee became
of no use, yet the English watchmakers, who siren
uously claim for their countryman. DR.. Hnke, the
glory of inventing the hair-spring, and who
the first to adopt the detached lever escapement,
still 90 making watches with fusees. and have
made very few without them.-[N B. Shipping
List.