THE PENDULUM CLOCK

BY CHRISTIAAN HUYGENS

OF ZUYLICHEM, SON OF CONSTANTIJN

THE OSCILLATING CLOCK,

CONCERNING THE MOTION OF PENDULUMS AS APPLIED TO CLOCKS

SIXTEEN years have now passed since we first made public the construction of the clocks we had then recently invented, by means of a small published book Huygens refers to his 1658 work, Horologium. Since that time, however, as we have discovered many things pertaining to the perfection of the work, it seemed best to set them all forth in this book. These findings indeed belong so much to the perfection of that invention that they may be considered its most powerful part, and as it were the foundation of this entire branch of mechanics, of which it was previously destitute. For a certain and equal measurement of time was not inherent in the nature of a simple pendulum, since wider swings are observed to be slower than narrower ones; but with geometry as our guide, we have discovered a different and previously unknown method of suspending the pendulum, having observed the curvature of a certain line The "certain line" is the cycloid, a curve that ensures the pendulum takes the same amount of time to swing regardless of the width of the arc, which is prepared in a truly wonderful manner to provide that desired equality to the motion. After which...