1 The Birth of Science - MSRI

116 4. Scientific Technology
that air expands when heated. It has a syphon that dips below water level
in two partly filled containers, one airtight and the other open. When the
air in the closed container is heated in the sun or by a fire, it pushes some
water through the syphon to the other container, and the opposite happens
when the temperature drops. Essentially the same object appears in
Heron’s Pneumatica, II, viii, where it is disguised as a fountain having the
amazing property of spouting only when it is exposed to the sun. The
same setup with a fire as the source of heat appears in I, xii, as a trick to
make automata pour libations onto an altar when a fire is lit. The construction
is repeated with sound effects — a hissing snake — in II, xxi.
At other times Heron refers to a preexisting technology with practical
uses when introducing a derived entertainment-related use. For example, page 158
in the Pneumatica, I, x, he explains one of his famous fountains, which relied
on pressure to create an astonishing gush of water. A key component
is the flap valve, which he introduces with the words “called an assarium
by the Romans”. He proceeds to describe the valve in detail in I, xi (though
it was obviously not a novelty), and uses it again in I, xxviii, in a pump
that serves as a fire extinguisher. The two constructions are very similar: in
either case a water jet is driven by air that is compressed thanks to pistons
and valves, and the basic designs largely coincide. Since we know that
Ctesibius invented this pump, we conclude that valves had been playing
a useful role for centuries, and that the purely ornamental fountain was an
offspring of the pump. Elsewhere Heron or one of his predecessors adapts
the mechanism of water clocks to light-hearted ends. Heron’s use of a paddlewheel
“like an anemourion” to operate a pipe-organ (page 109) may be
a further example of the same pattern.
Automata, which had been of interest since the third century B.C., are
precisely mechanisms able to transform a simple rotation into complex
motions, similar to those needed in human tasks. Mechanisms of this type
had been used from early Hellenistic times for military purposes and to
save labor, as we saw in the case of the repetition catapult and the sakiyeh.
We shall see in Section 9.3 examples of automation in agriculture during
the same period.
Now consider that eighteenth-century inventors did not just have, in
Dijksterhuis’ phrase, as many physical and technical possibilities as Heron:
they had the same possibilities. Because technology, like scientific theories,
is not predetermined by our genes, being rather a cultural product, this coincidence
should give us pause. It cannot but be due to the fact that at the
source of eighteenth-century technology lay the Hellenistic works, studied
since the twelfth century thanks above all to manuscripts available
through the Arabs in Spain, and later, more intensively, by Europeans in
general from the fifteenth century on. Thus it is that, in the early modern
Revision: 1.14 Date: 2002/10/24 04:25:47