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Watt steam engine
James Watt · 1776
The Watt steam engine is not a leap forward in power—it is a correction of thermal waste. It separates condensation from the cylinder so steam condenses cold while the cylinder stays hot. This cut coal use in half versus the Newcomen engine. But the 1776 version delivered only reciprocating motion for mine pumps. Rotary motion, double-acting operation, and expansive steam were later additions—not features of the original commercial engine.