What did I discover that so shocked me? When researching my last post on the inventors surrounding Prince Henry in the 1610s, and because I’ve been looking into the history of energy at the urging of Apoorv Sinha and others at Carbon Upcycling, I had a read through the published work of one of the inventors, Salomon de Caus.
De Caus often features in histories of the steam engine, as someone who in 1615 wrote about and depicted the expansive force of steam — heat up water in a copper vessel with a narrow tube coming out the top, and see how water or steam can be made to rise! He was even briefly known as the “true”, French inventor of the steam engine, because of a nineteenth-century hoax.
To historians of science and technology today, however, de Caus’s illustration is pretty unremarkable. He usually just gets a brief name-check, more or less copy-pasted from older histories. This is because the expansive force of steam would turn out not to be all that important in the development of the steam engine, as we’ll see, and because it was ancient.
3D animation of an aeolipile or Hero’s engine.
Animation by Michael Frey via Wikimedia Commons.
Hero of Alexandria, writing sometime in the first century, had already exploited the fact that when you boil the water in a metal vessel with a long, narrowing spout, the steam will come out with quite some force. This aeolipile, as it was sometimes called, was known and used throughout the middle ages and well into the seventeenth century. Sometimes it was shaped a bit like an alchemist’s retort, and known as the “philosophical bellows”. Other times, it was shaped as a human face, the steam issuing from its mouth — like the Greek god Aeolus, blowing the wind.
This was no mere toy, but found plenty of practical use. The spout of the philosophical bellows was often directed at a lamp’s flame, to have a sort of blow-torch effect. It was used, for example, to do finer tasks like bending glass pipes, or in fine metalwork — there are loads of accounts of this throughout the fifteenth, sixteenth, and seventeenth centuries, with some authors even talking about its merits relative to other instruments, suggesting real-life use. Its heat could, apparently, also be used to get fires going in wet weather, or from damp wood (provided you had some dry wood on hand to get the aeolipile itself going).
It could also be put to more sophisticated uses. Hero explained how the principle of thermal expansion — of either water or air — could be exploited to spout steam or even wine onto an altar’s fire to make it flare, to make water issue from a fountain, to make miniature dancers rotate and jump up and down, and to push air through bird-shaped automata to make them sing. A 1630s English version claimed to make the figure of a dragon hiss.
It could even be used to do some light mechanical work. Hero described a version that might make a hollow ball spin, by having the steam issue from bent nozzles. He even described a version where water could be forced by steam from one container into another, which would pull on a weight to open some doors. Taking his idea and running with it, engineers from at least the fifteenth century onwards wrote about directing the aeolipile’s narrow spout at miniature turbines to turn a roasting spits above a fire — suggested in Italy in Leonardo da Vinci’s notebooks, and in a 1551 Ottoman manuscript by Taqi ad-Din — or to do light industrial work like stamping ores and minerals into powders.
The principle of using heat to expand air or steam was even tried for much heavier-duty tasks. In 1605, the French inventor Marin Bourgeois developed an air-powered gun — known as the “wind-gun” — which used air that was pumped and compressed into the barrel. Within just a couple of years, having heard of the demonstration before the French court, and after paying a visit to Bourgeois, the mathematician David Rivault began experimenting on how the same effect might be achieved by heating water in a cannon. In the same decade, the Spanish military engineer Jerónimo de Ayanz y Beaumont also tried to use the expansionary force of steam to drive water up and out of mines — essentially, an industrial version of what Hero had done with fountains.
