Center of Gravity

I selected three flat river pebbles from the border of the garden path. Each possessed a different diameter and curvature. Sitting cross-legged on the smooth surface of a patio flagstone, I set the largest oval stone flat as a base. The second, slightly wedge-shaped, wobbled upon contact until I shifted its underside two millimeters toward the centerline. I lifted the third—a rounded black pebble no broader than my skull—and positioned it carefully at the apex. I withdrew both hands, fingers extended. The column swayed once, settled into friction, and remained motionless. Three tiers, aligned on a single vertical axis.