1 The Birth of Science - MSRI

112 4. Scientific Technology
automata were hidden from sight by automatically closing doors, which
opened a few seconds later to reveal a new arrangement.
Heron knows and uses precision screws, rack gears, reduction gears,
transmission chains, camshafts, 121 pistons, valves of various types, and
more. He puts to use many properties of fluids, the principle of jet propulsion
and the sources of natural power already mentioned: water, wind and
steam.
Conceptually, one of the most interesting features of Heron’s machines
is the pervasive presence of feedback mechanisms, capable of taking a system
back to its initial state after being displaced from it, or of maintaining
a device in a steady operation state (until the energy resource being used
is exhausted).
As we shall see in this section, modern attitudes toward Heron’s writings
have generally been misguided by the often amusing uses to which
he puts technology and by prejudices about classical civilization. A passage
of Dijksterhuis may be quoted as a good example of the common
opinion:
He has as many physical and technical possibilities at his command
as the eighteenth-century inventors who by their work made the industrial
revolution possible. Why, one is continually inclined to ask,
does he not accomplish anything comparable to their work, and why
does he confine himself to the construction of instruments without
any practical utility? 122
To see things in perspective, one must first of all recognize that the technology
described by Heron is too complex to be the creation of a single inventor.
When dealing with theoretical arguments, too, he appears as more
of a compiler and transmitter of information that as an innovator, and ever
more so as our knowledge of Hellenistic science advances. For instance, page 154
he was once considered the inventor of “algebraic” methods, but the decipherment
of cuneiform texts has shown that such methods had long been
in use in Mesopotamia; 123 Heron’s formula for the area of a triangle is attributed
to Archimedes by the Arabic mathematician al-Bīrūnī; 124 Heron’s
Definitions are avowedly a compilation made for divulgation purposes;
the principle of communicating vessels, though not discussed explicitly in
121 The cam (eccentric wheel) and camshaft convert circular motion into reciprocating (alternating
linear) motion. They were used, for example, in the pipe-organ already discussed on page 109
(Heron, Pneumatica, I, xliii). They were long thought to have been invented in medieval Europe or
in China.
122 [Dijksterhuis: MWP], p. 73.
123 On this topic see, for example, [Neugebauer: HAMA], vol. 2, p. 847.
124 [al-Biruni/Suter], p. 39.
Revision: 1.14 Date: 2002/10/24 04:25:47