A Chalk Line on Slate

I found a stub of pale blue sidewalk chalk resting in the seam between two flagstones just beyond the courtyard gate. Curious to see what mark it would leave, I picked up the chalk with both hands. It was powdery and light, its tip smoothed flat on one side. Bracing my boots against the rough stone, I leaned my weight forward and walked backward, dragging the chalk firmly across the dark slate. A crisp, dusty streak unfurled behind me, vivid and clean. After three steady paces, I set the chalk down right beside my line to take in the powdery trail.