Clock
an instrument for measuring and indicating the time of day. From the earliest periods of human history man has sought to measure time. To pastoral or agricultural nations where the duties by the four great divisions of sunrise, midday, sunset, and midnight, extreme measure of time was the sun-dial, but accuracy was not important. The first this being of no service at night or on cloudy days, the hour-glass was invented, this being of no service at night or on proved by the addition of a toothed wheel and index or sort of dial driven by the the jar. These have been in use 2,000 years. The next improvement was the turn the wheel. This has been attributed substitution of a weight for the water to turn the wheel. This has been attributed CLOCK necessary to regulate the weight so as to make the index pass over equal spaces in equal times. This must be accomplished by a pendulum or escapement of some kind, and a rude escapement is attributed to Gerbert, about A. D. 1000. A better one was that of De Vick in 1379.
Accuracy in marking time was not attained, however, by this, though it was a great improvement. For 270 years there was no advance, but between 1641 and 1658 the idea of attaching the pallets of the escapement to the pendulum-rod and making the escapement horizontal occurred both to Harris, an English clockmaker, and Huyghens, a Dutch philosopher. The anchor escapement of Dr. Hooke, invented in 1666-1680, and the dead-beat escapement of Graham in 1700, gave a new impulse to clockmaking. There has been no material change in the principles on which clocks are made, except in the substitution of steel springs for weights and in the finer movements, and addition of the hairspring to regulate still further the action of the escapement or pendulum, since 1700.
There have been a great variety of escapements invented and much more attention paid to accuracy in the details and perfection of finish, but the principles are the same.
Considered as scientific instruments for the precise measurement of time, they may be divided into two classes according to the character of the compensation of their pendulums, whether of the gridiron type or the mercurial pendulum. The CLOTHING The manufacture of clocks in America began about 1800 in Connecticut, which is still the center of the industry in the United States. legends say, having been given up to CLŒLIA, a girl of Rome, who, the Porsena as a hostage, escaped to Rome by swimming the Tiber.