What dependence did Galileo test experimentally using a long board with a gutter?

Galileo tested the dependence of distance on time experimentally using a long board with a groove. The board together with the stand formed an inclined plane. The experiment used balls of the same volume, made of different materials. In order to reduce the sliding resistance of the ball, the groove in the board was lined with parchment. In experiments, Galileo measured the time of movement of the ball with a water clock by the amount of water flowing out of the vessel through a small hole in it. He found that the displacements traversed by the balls along the inclined plane are proportional to the square of the time.