Steam, Its Generation and Use

While the time of man's first knowledge and use of the expansive force
of the vapor of water is unknown, records show that such knowledge
existed earlier than 150 B. C. In a treatise of about that time entitled
"Pneumatica", Hero, of Alexander, described not only existing devices of
his predecessors and contemporaries but also an invention of his own
which utilized the expansive force of steam for raising water above its
natural level. He clearly describes three methods in which steam might
be used directly as a motive of power; raising water by its elasticity,
elevating a weight by its expansive power and producing a rotary motion
by its reaction on the atmosphere. The third method, which is known as
"Hero's engine", is described as a hollow sphere supported over a
caldron or boiler by two trunnions, one of which was hollow, and
connected the interior of the sphere with the steam space of the
caldron. Two pipes, open at the ends and bent at right angles, were
inserted at opposite poles of the sphere, forming a connection between
the caldron and the atmosphere. Heat being applied to the caldron, the
steam generated passed through the hollow trunnion to the sphere and
thence into the atmosphere through the two pipes. By the reaction
incidental to its escape through these pipes, the sphere was caused to
rotate and here is the primitive steam reaction turbine.