> The engine in theory is double acting ie a pressure stroke is 
 > followed by a "vacuum" stroke.
 > 
 > I don't claim this as an invention, but probably read something in 
Good thing, too. It sounds a lot like the first steam engines (done by James 
Watt?) in England, used for pumping mines. They had essentially zero pressure 
steam, followed by a condensing water spray in the cylinder. There was no 
crankshaft as I recollect, just a sucker rod down the mineshaft to the 
pumping cylinder.
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