The Pendulum Clock

FIGURE I.

This diagram illustrates the internal gear train and the escapement mechanism that connects the power source to the pendulum.

FIGURE II.

This figure depicts the "cycloidal cheeks"—curved metal plates at the top of the pendulum suspension designed to ensure the clock keeps perfect time regardless of the width of the swing.

FIGURE III.

An external view of the completed wall clock, showing the integration of the internal mechanics into a functional 17th-century timepiece.

FIGURE IV.

A mathematical representation of the physics of a swinging body.

Center of oscillation original: "Centr. osc." — the point in a pendulum where all the mass could be concentrated without changing the period of its swing.
Center of gravity original: "Centr. gr." — the point at which the weight of the pendulum is balanced.

1 foot
2 feet
3 feet
15 seconds
30 seconds
45 seconds

The vocabulary below represents the core technical concepts introduced or refined by Huygens in this treatise.
Clock original: "Horologium", pendulum, center of oscillation, center of gravity, gear train, escapement, Christiaan Huygens, isochronism The property of a pendulum where the time taken for one swing remains constant even if the arc of the swing changes.