Vertical Assembly

Three flat slate pebbles were lying along the edge of the lawn. They were rough, but reasonably flat. I picked up the widest piece and placed it squarely on the flagstone. The second stone went on top. It leaned slightly to the right. I waited two seconds, then nudged it a quarter inch toward the center. It held. The third and smallest pebble completed the column. When I removed my hands, the stack did not sway. It stood four inches high beside my knee. We both remained upright in the garden.