An apparatus composed of a copper circle (diameter 38 cm) on a brass and wooden base (overall height 60 cm) with five brass balls that can slide on thin stretched wires, one along the vertical diameter and the others starting from the same point at the top but ending to the left and right of the vertical. A spring clamp allows all the balls to be held at the top of the wires. When released simultaneously, they reach the bottom simultaneously. They move with naturally accelerated motion but, while the one that falls vertically is subject to the acceleration of gravity, the others are subject to accelerations that are the components of the acceleration of gravity along their respective chords.
Since each chord is the projection of the vertical diameter along the direction of the chord, the relationship between the path travelled and the acceleration is the same for all the balls and, according to the law of naturally accelerated motion, the time employed must be the same.