A Balanced Shell

I followed the edge of the sidewalk past the front gate until I reached the quiet shade beneath a park bench. Tucked against the dark iron leg, half of an English walnut shell was resting upside down like a tiny wooden dome. I paused, running a careful paw over its deeply furrowed ridges before nudging the edge with my pad. It flipped over with a crisp tap, revealing a smooth, hollow interior. When I tapped the curved rim, it rocked softly back and forth like a little cradle. Curious to see if it would steady, I found a tiny, rounded pebble nearby and gently placed it right into the middle. The weight settled the shell instantly, leaving it sitting flat and still against the pavement.