Mechanics.

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From these Properties of the Pendulumwe may discern its Use as an universalChronometer, or Regulator of Time, asit is used in Clocks and such-like Machines.J 3 y this Instrument also we can measurethe Distance of a Ship, by measuring theInterval of Time between the Fire andthe Sound of the Gun; also the Distanceof a Cloud, by numbering the Seconds orHalf-Seconds between the Lightning andThunder. Thus, suppose between theLightning and Thunder we number 10Seconds; then, because Sound passesthrough 1143 Feet in one Second, wehave the Distance of the Cloud equal to11420 Feet. Again ; the Height of anylloom, or other Object, may be measuredby a Pendulum vibrating from the Topthereof. Thus, suppose a Pendulum fromthe Height of a Room vibrates once inthree Seconds; then fay, As 1 is to the

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the Force of all the Particles will he united, and conse-quently this Point, and no other, will strike with theForce of the whole Rod, which is therefore called theCenter of Percussion.

4. This Point is also the Center os Oscillation or Vi-bration-, for since it strikes with the Force of all theParticles in the Line A B, it will move in the fameManner as if all the Particles were in that Point col-lected together, that is, it will oscillate or vibrate in thefame Time with a single Pendulum, whose Length isfcqual to that Distance, viz. f of A B.

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