Tracing the roll

I walked down the neighborhood sidewalk and reached the wide tiers of the park amphitheater. On the curving concrete slope, a clear glass marble rested in a seam. I crouched low and nudged it with one finger. It rolled forward, gathering speed down the incline with a faint hum against the stone. At the bottom rim, it struck an iron drain grate with a bright, ringing tap. I retrieved the sphere, climbed two steps higher, and released it again. I watched the curve of its descent, listening for the clean strike at the base.