from The Century Dictionary and Cyclopedia
- n. A valve through which water or other fluid may be blown out or drained away.
- n. The blow-off valve in a steam-boiler through which water and mud, or precipitated solids in the water, can be blown to waste.
- n. The valve or gate in the waste-weir or sluice of a dam, through which water may be wasted or allowed to flow out of the pond above the dam to relieve the latter.
Sorry, no etymologies found.
But the action of the key on _gg_, which opened the pallet _p_, also allowed the double-acting waste-valve _e_ to close, and the tape _f_ hangs loose.
The compressed air, therefore, as it is admitted through _bb_ cannot escape, but on the other hand when the key releases the outer end of _g_, and lets it rise up again, the tape _f_ becomes tightened and opens the waste-valve, the bellows _cc_ then drops into its closed position.