Heronís Steamboat

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    Imagine walking along the Nile River somewhere not far south of the Delta, sometime in the middle of the First Century A.D. This is Roman Egypt and weíre not far from Alexandria, one of the great centers of learning in the Roman Empire. We notice immediately how quiet this world sounds. All we hear are animal sounds, peopleís voices, and an occasional splash from the river, none of their sources close at hand.

    Suddenly we hear a loud shriek, as if a hawk had emitted its cry immediately into our ears. Startled, we look toward the source of the noise and see a strange-looking craft moving up the river.

    Itís a boat of some kind, but it doesnít look like any of the other boats on the river. It doesnít have a mast and sail and it doesnít have teams of men rowing. Instead, it bears a kind of tower from which smoke rises into the air. On each side thereís a large chariot wheel that has paddles attached to it and itís turning, making the boat look like itís rolling upstream. People near the river are standing and gazing at the thing in awe. We hear several people ask, "What is it? What makes it move? Without a sail, without rowers, how does it move?"

    With our modern perspective we recognize the craft as a crude form of sidewheel steamboat. Hidden within the hull lies a steam engine that turns the paddlewheels. The force that the paddles exert on the water as the wheels turn yields a reaction force, in accordance with Mr. Newtonís third law of motion, that pushes the boat upriver.

    But surely thatís an impossible vision. Certainly, we think, there was no way in which anyone in First Century Egypt could have achieved the goal of building a functioning steamboat, even if they had been able to conceive the idea of such a thing. We think that thought because we have come to think that, because they didnít have our extensive knowledge and our powerful machines, our ancestors were less clever than us. That thought has even spawned a minor industry based on people declaring that our ancestors were so weak and stupid that only alien astronauts could have built the large structures, such as the great pyramids on the Giza Plateau overlooking Cairo, that we see scattered around Earth today. Thatís arrant nonsense, of course: you would have to go back thousands of centuries to find human ancestors who had noticeably less brainpower than we do.

    More to the point, there actually was someone in Roman Egypt who could have designed a simple steamboat that Egyptian workers could have built and operated. His name was Heron and he taught mathematics, physics, mechanics, and pneumatics at the Musaeum (House of the Muses) in Alexandria, just west of the Delta. He is best known for the Aeolipile (ah-OH-luh-pill-ee comes closest to the correct Greek pronunciation), a simple steam engine that consisted of a hollow sphere (the ball of Aeolus) with a pair of nozzles jutting from its equator and a pair of tubes poking through bearings at the poles. When steam entered the ball through the tubes and blew out through the nozzles the ball turned.

    Among other devices that Heron invented we find the windwheel. It apparently looked a little bit like the windmills that we would have found on most American farms in the late Nineteenth Century and early Twentieth Century. When wind blew through it, it turned and in turning drove a pump that indirectly operated a simple pipe organ. Heron had something else that he could have used to turn the windwheel, if only he had conceived the idea of it: he could have set up nozzles, like those on the aeolipile, to blow steam on the wheel and thereby run the windwheel as a crude steam turbine.

    Why did he not conceive the idea? He certainly had the incentive to do so. The windwheel depended upon the vagaries of Nature. When the wind stopped blowing, whatever the windwheel was driving stopped working. But a steamwheel would have been entirely under human control. All it required was someone to produce and maintain the fire and to ensure that the boiler was full. But fire was a relatively rare commodity in Egypt, due to the scarcity of fuel (Fire was used primarily for cooking and illumination and little else.). A subconscious understanding of that fact may have exerted an inhibitory influence on thoughts pertaining to the invention of fire-driven machines. The idea of a steamwheel simply may not have entered Heronís conscious mind.

    Conception of the idea of the paddlewheel may have been similarly inhibited. At that time the wheel was almost entirely a passive device. It supported vehicles and enabled them to move more or less smoothly across the landscape. There were also some minor applications in which the Romans used hollow wheels with slaves walking inside them to lift things. But the idea of a wheel pushing something would have been new: the idea of applying a torque to an axle to make a wheel move would have been new. Of course, the windwheel already turned an axle (its own), but the idea of attaching a second wheel to the axle and making it move something might not have been obvious.

    The idea of putting paddles on a wheel, especially if Heron had never seen nor heard of a waterwheel, might have been similarly inhibited. In the ancient mind a paddle was a thing that a man uses to push against water in a reciprocating motion. The idea of a paddle going round and round might have been too alien for Heron to conceive; all the more so because, until he could conceive the steamwheel as a driver, he would have no way to power it.

    We might think that Heron could devise an intermediate means of providing power by thinking of attaching a crank to the paddlewheelís axle so that a man could use it to turn the wheel. But we have no evidence that anyone in Egypt or Europe knew about the crank prior to the Second Century A.D. That fact makes it difficult to have a transitional form of the paddlewheel in the First Century. However, in the Fifteenth Century, whose technology differed little from that of the Roman Empire, an artist called Anonymous of the Hussite Wars painted a picture of two men propelling a boat by cranking two pairs of paddlewheels, so the idea would not have been completely outrageous.

    Another factor in Heronís not conceiving the idea of a steamboat comes from our way of categorizing things. In the category "Things that Move Boats" Heron would have put sails and men rowing with paddles or oars. But would there have been room in that category for wheels turning paddles? If the idea was too alien, it might not have fit and Heron simply would not have conceived the idea of the new propulsion system.

    On the other hand, we think, there was an incentive that opposed those countervailing influences and would have rewarded Heron for coming up with the idea of a wholly new kind of boat. There was a practical value in a steamboat, if only to enable the ruling class to better display their power and glory. Alas, practicality was not an appealing value in Heronís mind.

    In those days philosophers didnít think in practical terms. Philosophy was meant solely for the improvement of the mind, and not for the improvement of commerce or any other parts of daily life. But suppose Heron had been more accommodating of practical applications; suppose that he had seen an opportunity to show what philosophy could achieve in the real world. Attitude counts in the advancement of civilization.

    Nonetheless, letís assume that by a fantastic stroke of luck Heron conceived the idea for a steamboat and that craftsmen built one for him to try out on the Nile. By First Century standards, thatís going to be one spectacular ride. But then itís going to hit a barrier, the same one that stopped Nicholas-Joseph Cugnot in 1771.

    We remember Cugnot as the poor clown who made the first, pathetic attempt to invent the automobile. His steam dray, first built in 1769, looks like a joke: it consisted of a three-wheeled carriage with a large kettle hanging from a bar jutting over the front wheel. But Cugnotís steam dray worked as intended: weighing 2.5 tonnes, it carried 4 tonnes of cargo at a speed of about 2-1/2 miles per hour, fast enough to keep up with a marching army. What killed it was the fact that it had to stop every fifteen minutes to allow the engineer to refill the boiler and rebuild the fire. Heronís steamboat would have encountered the same problem.

    Steam-powered propulsion had to wait until someone devised a way to refill the boiler while it was still under pressure and to keep the fire burning continuously. It was that devising that led to the invention of actual steamboats and steam locomotives at the beginning of the Nineteenth Century.

    Heron could have made that leap of invention and others as well. He certainly possessed sufficient knowledge to make the inventions that he would have needed. We also know from the devices that were made for him that the craftsmen of the time possessed the means and the skill to make what he needed. What he lacked was a proper focus, an ability to conceive things that would improve his world and to then find the steps that he needed to take to create that improvement. That is where culture intersects with engineering.


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