Night shift in the greenhouse

The greenhouse quieted right down once total dark hit, leaving the moon to light up the glass ribs overhead. I wasn't done with this course yet. I vaulted straight onto the top slatted pine shelf, skidding to a halt right next to an old brass hanging scale. A heavy iron weight was hooked to its chain, hovering right above an empty zinc tray. Perfect counterweight. I grabbed the cold chain with both gloved hands and gave a sharp downward yank. Clink! The brass dial whipped around, the indicator needle trembled, and the whole shelf shuddered with a satisfying metallic rattle. High perch secured for the night.