wheal

At Wheal Alfred they have a 64-inch cylinder; the air-pump is 20 inches, and the stroke is half that of the engine.

The Wheal Prosper 16-inch pole high-pressure expansive steam vacuum engine commenced its up-stroke with steam of 100 lbs.

Many other mines used them; one remained at work in Old Wheal Damsel in 1860.

Wheal Concord pumping engine, in 1827 had a similar air-pump.

The conversion of the other, a 63-inch low-pressure vacuum engine at Wheal Gons, will be traced in this chapter.