The Genesis of Steam

摘要

The ancient Greeks and Romans were not only among the first to discover the value of guided trackways (see chapter one). To their extraordinarily advanced civilisation must also be credited the first investigation of gases. Philo of Byzantium (3rd century BC) and Hero of Alexandria (1st century AD) both understood that air expands when heated and contracts when cooled. They also understood that steam expands, though perhaps not that it contracts when condensed. And they had some notion of vacuum. They tested their ideas in the laboratory and in small-scale working gadgets, most famously in Hero's 'Aeolipile' reaction turbine rotated by jets of steam. But no practical application was at that time possible. i