In the fall of 1880 I was encamped on the Kaibab plateau above the canyon gorge of a little stream. White men and Indians composed the party with me. Our task was to make a trail down this side canyon, which was many hundreds of feet in depth, into the depths of the Grand Canyon of the Colorado. While in camp after the days work was done, both Indians and white men amused themselves by attempting to throw stones across the little canyon. The distance from the brink of the wall on which we were encamped to the brink of the opposite wall seemed not very great, yet no man could throw a stone across the chasm, though Chuar, the Indian chief, could strike the opposite wall very near its brink. The stones thrown by others fell into the depths of the canyon. I discussed these feats with Chuar, leading him to an explanation of gravity. Now Chuar believed that he could throw a stone much farther along the level of the plateau than over the canyon.