CHAP. VI.
CORRESPONDENCE OF WATT WITH SMEATON.—FAILURE OF CONDENSATION BY SURFACE.—IMPROVEMENTS IN CONSTRUCTION OF PISTON.—METHOD OF PACKING.—IMPROVEMENTS IN BORING THE CYLINDERS.—DISADVANTAGES OF THE NEW COMPARED WITH THE OLD ENGINES.—GREATLY INCREASED ECONOMY OF FUEL.—EXPEDIENTS TO FORCE THE NEW ENGINES INTO USE.—CORRESPONDENCE WITH SMEATON.—EFFICIENCY OF FUEL IN THE NEW ENGINES.—DISCOVERY OF THE EXPANSIVE ACTION OF STEAM.—WATT STATES IT IN A LETTER TO DR. SMALL.—ITS PRINCIPLE EXPLAINED.—MECHANICAL EFFECT RESULTING FROM IT.—COMPUTED EFFECT OF CUTTING OFF STEAM AT DIFFERENT PORTIONS OF THE STROKE.—PRODUCES A VARIABLE POWER.—EXPEDIENTS FOR EQUALISING THE POWER.—LIMITATION OF THE EXPANSIVE PRINCIPLE IN WATT'S ENGINES.—ITS MORE EXTENSIVE APPLICATION IN THE CORNISH ENGINES.
