concerning how a toy built in Alexandria failed to inspire, and how a glass tube made in Italy succeeded; the spectacle of two German hemispheres attached to sixteen German horses; and the critical importance of nothing at all
TO GET TO CROFTON from Birmingham, you take the M5 south about sixty miles to Brockworth and then change to the A417, which meanders first east, then southwest, then southeast, for another forty-six miles, changing, for no apparent reason, into the A419, and then the A436. In Burbage, you turn left at the Wolfhall Road and follow it another mile, across the railroad tracks and over the canal. The reason for making this three-hour journey (not counting time for wrong turns) is visible for the last quarter-mile or so: two red brick buildings next to a sixty-foot-tall chimney.
The Crofton Pump Station in Wiltshire contains the oldest steam engine in the world still doing the job for which it was designed. Every weekend, its piston-operated beam pumps twelve tons of water a minute into six eight-foot-high locks along the hundred-mile-long Kennet and Avon Canal. The engine itself, number 42B—the figure “B.42” is still visible on the engine beam—is so called because it was the second engine with a forty-two-inch cylinder produced by the Birmingham manufacturer Boulton & Watt. It was entered in the company’s order book on January 11, 1810, and installed almost precisely two years later. Except for a brief time in the 1960s, it has run continuously ever since.
First encounters with steam power are usually unexpected, inadvertent, and explosive; the cap flying off a defective teakettle, for example. No surprise there; the expansive property of water when heated past a certain point was known for thousands of years before that point was ever measured, and to this day it’s what drives the turbine that generates most of our electricity, including that used to power the light by which you are reading this book. The relationship between the steam power of a modern turbine and the kind used to pump the water out of the Kennet and Avon Canal is, however, anything but direct. By comparison, the mechanism of engine 42B is a thing of Rube Goldberg–like complexity, with levers, cylinders, and pistons yoked together by a dozen different linkages, connecting rods, gears, cranks, and cams, all of them moving in a terrifyingly complicated dance that is at once fascinating, and eerily quiet—enough to occupy the mechanically inclined visitor, literally, for hours. When the engine is “in steam,” it somehow causes the twenty-six-foot-long cast iron beams to move, in the words of Charles Dickens, “monotonously up and down, like the head of an elephant in melancholy madness.”
There is, however, something odd about the beams, or rather about the pistons to which they are attached. The pistons aren’t just being driven up by the steam below them. The power stroke is also down: toward the steam chamber. Something is sucking the pistons downward. Or, more accurately, nothing is: a vacuum.
Using steam to create vacuum was not the sort of insight that came an instant after watching a teakettle lid go flying. It depended, instead, on a journey of discovery and diffusion that took more than sixteen centuries. By all accounts the trip began sometime in the first century CE, on the west side of the Nile Delta, in the Egyptian city of Alexandria, at the Mouseion, the great university at which first Euclid and then Archimedes studied, and where, sometime around 60 CE, another great mathematician lived and worked, one whose name is virtually always the first associated with the steam engine: Heron of Alexandria.
The Encyclopaedia Britannica entry for Heron—occasionally, Hero—is somewhat scant on birth and death dates; as is often the case with figures from an age less concerned with such trivia, it uses the abbreviation “fl.” for the latin floruit, or “flourished.” And flourish he did. Heron’s text on geometry, written sometime in the first century but not rediscovered until the end of the nineteenth, is known as the Metrika, and includes both the formula for calculating the area of a triangle and a method for extracting square roots. He was even better known as the inventor of a hydraulic fountain, a puppet theater using automata, a wind-powered organ, and, most relevantly for engine 42B, the aeolipile, a reaction engine that consisted of a hollow sphere with two elbow-shaped tubes attached on opposite ends, mounted on an axle connected to a tube suspended over a cauldron of water. As the water boiled, steam rose through the pipe into the sphere and escaped through the tubes, causing the sphere to rotate.
Throughout most of human history, successful inventors, unless wealthy enough to retain their amateur status, have depended on patronage, which they secured either by entertaining their betters or glorifying them (sometimes both). Heron was firmly in the first camp, and by all accounts, the aeolipile was regarded as a wonder by the wealthier classes of Alexandria, which was then one of the richest and most sophisticated cities in the world. Despite the importance it is given in some scientific histories, though, its real impact was nil. No other steam engines were inspired by it,1 and its significance is therefore a reminder of how quickly inventions can vanish when they are produced for a society’s toy department.
In fact, because the aeolipile depended only upon the expansive force of steam, it should probably be remembered as the first in a line of engineering dead ends. But if the inspirational value of Heron’s steam turbine was less than generally realized, that of his writings was incomparably greater. He wrote at least seven complete books, including Metrika, collecting his innovations in geometry, and Automata, which described a number of self-regulating machines, including an ingenious mechanical door opener. Most significant of all was Pneumatika, less for its descriptions of the inventions of this remarkable man (in addition to the aeolipile, the book included “Temple Doors Opened by Fire on an Altar,” “A Fountain Which Trickles by the Action of the Sun’s Rays,” and “A Trumpet, in the Hands of an Automaton, Sounded by Compressed Air,” a catalog that reinforces the picture of Heron as antiquity’s best toymaker) than for a single insight: that the phenomenon observed when sucking the air out of a chamber is nothing more than the pressure of the air around that chamber. It was a revelation that turned out to be utterly critical in the creation of the world’s first steam engines, and therefore of the Industrial Revolution that those engines powered.
The idea wasn’t, of course, completely original to Heron; the idea that air is a source of energy is immeasurably older than science, or even technology. Ctesibos, an inventor and engineer born in Alexandria three centuries before Heron, supposedly used compressed air to operate his “water organ” that used water as a piston to force air through different tubes, making music.
Just as the ancients realized that moving air exerts pressure, they also recognized that its absence did something similar. The realization that sucking air out of a closed chamber creates a vacuum seems fairly obvious to any child who has ever placed a finger on top of a straw—as indeed it was to Heron. In the preface to Pneumatika, he wrote,
if a light vessel with a narrow mouth2 be taken and applied to the lips, and the air be sucked out and discharged, the vessel will be suspended from the lips, the vacuum drawing the flesh towards it that the exhausted space may he filled. It is manifest from this that there was a continuous vacuum in the vessel….
thus producing what a modern scholar has called a “very satisfactory theory3 of elastic fluids.”
Satisfactory to a twenty-first-century child, and a first-century mathematician, but not, unfortunately, for a whole lot of people in between. To them, the idea that space could exist absent any occupants, which seems self-evident, was evidently not, and the reason was the dead hand of the philosopher-scientist who tutored Alexandria’s founder. Aristotle argued against the existence of a vacuum with unerring, though curiously inelegant, logic. His primary argument ran something like this:
1. If empty space can be measured, then it must have dimension.
2. If it has dimension, then it must be a body (this is something of a tautology: by Aristotelian definition, bodies are things that have dimension).
3. Therefore, anything moving into such a previously empty space would be occupying the same space simultaneously, and two bodies cannot do so.
More persuasive was the argument that a void is “unnecessary,” that since the fundamental character of an object consists of those measurable dimensions, then a void with the same dimensions as the cup, or horse, or ship occupying it is no different from the object. One, therefore, is redundant, and since the object cannot be superfluous, the void must be.
It takes millennia to recover from that sort of unassailable logic, temptingly similar to that used in Monty Python and the Holy Grail to demonstrate that if a woman weighs as much as a duck, she is a witch. Aristotle’s blind spot regarding the existence of a void would be inherited by a hundred generations of his adherents. Those who read the work of Heron did so through an Aristotelian scrim on which was printed, in metaphorical letters twenty feet high: NATURE ABHORS A VACUUM.
Given that, it is something of a small miracle that Pneumatika, and its description of vacuum, survived at all. But survive it did, like so many of the great works of antiquity, in an Arabic translation, until around the thirteenth century, when it first appeared in Latin. And it was another three hundred years until a really influential translation arrived, an Italian edition translated by Giovanni Batista Aleotti d’Argenta and published in 1589. Aleotti’s work, and subsequent translations4 of his translation into German, English, and French (plus five more in Italian alone), demonstrate both the demand for and availability of the book. Aleotti, an architect and engineer, was practical enough; in his annotations to his translation of the Pneumatika, he mentions the difficulty of removing a ramrod from a cannon with its touchhole covered because of the pressure of air against the vacuum therefore created—a phenomenon that could only exist if air were compressible and vacuum possible. It is testimony to the weight of formal logic5 that even with the evidence in front of his nose, Aleotti was still intellectually unable to deny his Aristotle.
If Aleotti was unaware of the implications of Heron’s observations, he was indefatigable in promoting them, and by the seventeenth century, it can, with a wink, be said that Pneumatika was very much in the air, in large part because of the Renaissance enthusiasm for duplicating natural phenomena by mechanical means, the era’s reflexive admiration for the achievements of Greek antiquity. The scientist and philosopher Blaise Pascal (who modeled his calculator, the Pascaline, on an invention of Heron’s) mentioned it in D’esprit géometrique, as did the Oxford scholar Robert Burton in his masterpiece, Anatomy of Melancholy: “What is so intricate,6 and pleasing as to peruse … Hero Alexandrinus’ work on the air engine.” But nowhere was Aleotti’s translation more popular than the city-state of Firenze, or Florence.
Florence, in the year 1641, had been essentially the private fief of the Medici family for two centuries. The city, ground zero for both the Renaissance and the Scientific Revolution, was also where Galileo Galilei had chosen to live out the sentence imposed by the Inquisition for his heretical writings that argued that the earth revolved around the sun. Galileo was seventy years old and living in a villa in Arcetri, in the hills above the city, when he read a book on the physics of movement titled De motu (sometimes Trattato del Moto) and summoned its author, Evangelista Torricelli, a mathematician then living in Rome. Torricelli, whose admiration for Galileo was practically without limit, decamped in time not only to spend the last three months of the great man’s life at his side, but to succeed him as professor of mathematics at the Florentine Academy. There he would make a number of important contributions to both the calculus and fluid mechanics. In 1643, he discovered a core truth in the behavior of liquids in motion, known as Torricelli’s theorem, that is still used to calculate the speed of a fluid when it exits the vessel that contains it. He made fundamental contributions to the development of the calculus, and to the geometry of the cycloid (the path described by a point on a rolling wheel). Less typically, he embarked on a series of investigations whose results were, literally, revolutionary.
In those investigations, Torricelli used a tool even more powerful than his well-cultivated talent for mathematical logic: He did experiments. At the behest of one of his patrons, the Grand Duke of Tuscany, whose engineers were unable to build a sufficiently powerful pump, Torricelli designed a series of apparatuses to test the limits of the action of contemporary water pumps. In spring of 1644, Torricelli filled a narrow, four-foot-long glass tube with mercury—a far heavier fluid than water—inverted it in a basin of mercury, sealing the tube’s top, and documented that while the mercury did not pour out, it did leave a space at the closed top of the tube. He reasoned that since nothing could have slipped past the mercury in the tube, what occupied the top of the tube must, therefore, be nothing: a vacuum.
Even more brilliantly, Torricelli reasoned, and then demonstrated, that the amount of space at the top of the tube varied at different times of the day and month. The only explanation that accounted for his observations was that the variance was caused by the pressure of air; the more pressure on the open reservoir of mercury at the base of the tube, the higher the mercury rose within. Torricelli had not only invented,7 more or less accidentally, the first barometer; he had demonstrated the existence of air pressure, writing to his colleague Michelangelo Ricci, “I have already called attention to certain philosophical experiments that are in progress … relating to vacuum, designed not just to make a vacuum but to make an instrument which will exhibit changes in the atmosphere … we live submerged at the bottom of an ocean of air….”
Torricelli was not, even by the standards of his day, a terribly ambitious inventor. When faced with hostility from religious authorities and other traditionalists who believed, correctly, that his discovery was a direct shot at the Aristotelian world, he happily returned to his beloved cycloids, the latest traveler to find himself on the wrong side of the boundary line between science and technology.
But by then it no longer mattered if Torricelli was willing to leave the messiness of physics for the perfection of mathematics; vacuum would keep mercury in the bottle, but the genie was already out. Nature might have found vacuum repugnant for two thousand years, but Europe was about to embrace it.
ON NOVEMBER 20, 1602, in Magdeburg, a town in Lower Saxony, hard by the Elbe River, the former Anna von Zweidorff, by then the wife of a prosperous landowner named Hans Gericke, gave birth to a son, Otto. This was something like being born in Mogadishu, Somalia, in 1975: When Otto was sixteen years old, the armies of the last great religious war in European history began marching and countermarching across Germany, enforcing orthodoxy at the end of a pike in what became known as the Thirty Years War. Magdeburg, which had been a bastion of Protestantism ever since Martin Luther had visited in 1524, became a target for the armies of the Catholic League, not once, but half a dozen times; in 1631, the troops of Count Johann Tilly sacked the city, killing more than twenty thousand. By the time the various treaties that comprised the Peace of Westphalia were signed in 1648, the city was home to fewer than five hundred war-weary survivors. One of them was Otto Gericke, home from his studies in Leipzig, Jena, and Leiden, now a military engineer who was enlisted to help rebuild the city, and had been named one of its four mayors. He was, entirely as one might expect, eager to turn his talents to more peaceful pursuits.
Though evidently unaware of the details of Torricelli’s experiments, he was headed down the same path, intending to demonstrate the power of a vacuum and therefore the weight of air. By 1650 or so, he had built the Magdeburger windbüchse, which looked like a gun but worked like a vacuum pump, a piston encased in a cylinder with an ingenious one-way flap valve that kept the cylinder airtight once the piston was withdrawn and was rightly regarded as one of the “technical wonders of its time.”8 It was, however, barely an appetizer for what came next. For in 1652, Gericke, fascinated by the elasticity and compressibility of air, was to produce some of the most famous experimental apparatuses in history.
The original copper objects that came to be known as the Magdeburg hemispheres are on view at the Deutsches Museum in Munich, looking today a bit like oversized and battered World War I army helmets, with a dark bronze patina caused by nearly four hundred years of oxidation. Ropes dangle from half a dozen iron fasteners on both, and one holds a tube designed to mate with Gericke’s vacuum pump. When Gericke constructed them in 1665, the ropes were tied to the harnesses of a team of horses, and the copper shone like a mirror. The reasons had more to do with theater than science. With the smooth rims of the hemispheres coated with grease, the air pumped out of the globe, and the horses urged in opposite directions, the show was irresistible. Its first appearance was in 1654, in front of the Imperial Diet in Regensburg, where Gericke tied his ropes to thirty horses—fifteen attached to either hemisphere—and demonstrated their inability to pull the pieces apart. That was followed by similar entertainments in 1656 in Magdeburg (with sixteen horses), in 1657 before the emperor’s court in Vienna, and most famously of all, in 1664, before the German elector Friedrich Wilhelm, who was amazed to see twenty-four horses straining to pull apart a twenty-inch globe held together only by air pressure.*
The Magdeburg hemispheres are deservedly some of the most famous experimental devices of all time, and versions are still used in science classrooms to this day. But their fame owes at least as much to showmanship as to any intrinsic contribution to the physics of vacuum. In 1661, Gericke performed a far more sophisticated, though less well remembered, experiment. It consisted of two suspended platforms connected by a single rope, each under a pulley, with both pulleys suspended from a horizontal beam. On one he placed an airtight chamber with a close-fitting piston; on the other, a measured amount of lead weight. As the air was pumped out of the chamber,9 the piston was forced down by the weight of atmosphere, and the weight raised by the same amount—the first practical application of the power of the vacuum, well recounted in his 1672 book, Experimenta nova, ut vocantur, Magdeburgica de vacuo spatio.
But it was the hemispheres that, in the end, mattered. They are the reason Emperor Leopold I knighted Gericke in 1666, making him Otto von Guericke (including the unexplained introduction of the u to his name). It was the hemispheres that a German Jesuit and mathematician named Gaspar Schott saw at the 1654 demonstration, and that initiated an admiring correspondence between Schott and Gericke. And it was the hemispheres that were featured in Schott’s 1657 book, with the intimidating title Mechanicahydraulica-pneumatica, which contained a description of both the vacuum pump and the hemispheres (and included a drawing eerily similar to the logo used by Levi Strauss to testify to the inability of even whipped horses to pull a pair of jeans apart). And of course the hemispheres mark another fork in the road for the idea powering engine 42B on its way from continental Europe to Britain, where Schott’s book traveled almost as soon as it was published.
ENGLAND, IN THE MIDDLE of the seventeenth century, had not witnessed the brutal devastation that had been visited upon Gericke’s homeland by the Thirty Years War, but it had not exactly been a model of peaceful coexistence either. A dispute between King and Parliament10 over their respective degrees of authority exploded into civil war in 1643; it had been temporarily suspended by the execution of Charles I and the exile of his son, Charles II, but not before a hundred thousand men, women, and children were dead. One of the Civil War’s less dramatic but equally far-reaching consequences was that the various colleges at Oxford, which had been the king’s base of operations for much of the war, had walked a delicate line between their traditional and reflexive support for the monarchy and prudent obedience to its replacements: first the Commonwealth, and then the de facto dictatorship of Oliver Cromwell. By the time England, and Oxford, had received copies of Schott’s book, they had been without a king for years, and the town’s scholars, two in particular, were more interested in persuading nature to give up her secrets than in forcing their countrymen to choose a sovereign.
It seems almost indecently apt that Robert Hooke and Robert Boyle were among the first, and certainly the most important, Englishmen to learn of Gericke’s experiments. The aptness is not due entirely to their interest in vacuum; these wildly inventive, almost ridiculously prolific men were interested in practically everything. A brief list of their respective achievements would include the discovery of the Law of Elasticity; the founding of the science of experimental chemistry; the invention of the microscope; the discovery of the basic law governing the behavior of gases; the first observation of the rotation of both Jupiter and Mars; the discovery of the inverse-square law of gravity; the authorship of some of the seventeenth century’s most profound Christian apologetics; and the founding of the world’s first scientific society.
Their link began in 1659 or so, when Boyle, a brilliant and wealthy aristocrat, hired Hooke, a brilliant and impecunious scholarship student, to improve on Gericke’s vacuum pump. The improvement that Boyle had in mind was critical: He needed a machine that would not merely demonstrate the existence of a vacuum for the entertainment of European aristocrats, but would allow him to investigate its characteristics. Hooke’s answer was the machine Boyleana, an experimental device that would reveal what was happening inside the vacuum chamber and allow manipulation of it. Boyle had earlier hired the now forgotten Ralph Greatorex (“the leading pumping engineer in England”11) to achieve these goals, but where he had failed, Hooke succeeded. His design incorporated a glass vessel and two cone-shaped brass stoppers that, when coated with oil, could be rotated, pulling a thread that could be attached to the clapper of a bell, the wick of a candle—to anything, in short,12 that might be part of a viable experiment on the nature of vacuum.
All by itself, Hooke and Boyle’s series of vacuum experiments, described in the 1660 publication of New Experiments Physico-Mechanical, Touching the Spring of the Air and Its Effects, would have bought them an entry in the history of steam power. In their hands, the machine Boyleana made basic discoveries into the properties of sound—when air was removed from the chamber, so too was the sound of a bell within it—of animal respiration, and of combustion. The experiments conducted by the two men produced the law of physics that still bears Boyle’s name,* and the demonstration that the volume of a gas at constant temperature is inversely proportional to pressure (with the corollary that increasing temperature equals increased pressure) is an insight of some significance for the road leading from Torricelli’s mercury tube to engine 42B.
However, the most significant characteristic of the two men’s work—the one that best reveals why the road to steam power was thereafter almost entirely an English one—is the fact that Boyle hired Hooke.
BEGIN WITH THEIR BEGINNINGS: Robert Boyle was one of the younger sons of an earl, born in Lismore Castle and educated at Eton, in Switzerland, and in France. By the time he returned from Florence in 1642 (where he read Galileo’s Dialogue on the Two Chief World Systems and began a lifelong devotion to mechanical explanations: in his words “those two grand and most catholic principles, matter and motion”13), his father had died, leaving him a Dorsetshire manor and sufficient income from his Irish estates to study whatever part of “matter and motion” took his fancy. Hooke was born to a modest curate on the Isle of Wight, who left him just enough to purchase an apprenticeship with a portrait painter. Boyle arrived in Oxford in 1654 as a gentleman scholar; Hooke made his way to Oxford a year later, a scholarship student eager for anything to supplement his very modest stipend.
The two did share an affinity for the royalist cause, though not especially for the High Anglicanism associated with it. Boyle, in particular, was a devoted Protestant, well remembered for his piety, who famously argued (in The Christian Virtuoso) that devoutness did not forbid study of natural phenomena, but rather demanded it. His advocacy of experiment and experience—in brief, empiricism—as the best method for explaining the world was partly a response to the materialism (halfway to atheism,14 in the view of Boyle’s Oxford colleague, Seth Ward) of Thomas Hobbes, who returned the favor, sneering at Boyle’s work, which he called “engine philosophy.”15
Robert Hooke’s philosophy, on the other hand, seems to have been driven more by a need for recognition than salvation. For all his extraordinary range of achievements (not only was he Christopher Wren’s surveyor and colleague during the rebuilding of London after the Great Fire of 1666, an early advocate of evolutionary theory, the first to see that organic matter was made up of the building blocks that he named “cells,” and probably England’s most gifted mathematician,16 able to turn his hand to everything from describing the catenary curve of the ideal arch to the best way to trim sails), he is frequently remembered today, as he was known during his lifetime, as the world’s best second fiddle. The shadow cast by Wren, by Boyle, and even by Isaac Newton, with whom Hooke engaged in a long-running and ultimately futile dispute over the authorship of the law of gravitational attraction, is unaccountable without considering the class difference between them. James Aubrey, the seventeenth-century memoirist, paid Hooke something of a backhanded compliment when he called him “the best Mechanick this day in the world.”17
When the informal assembly at Oxford whose meetings were generally led by the clergyman John Wilkins was chartered, two years after the Restoration of Charles II in 1660, as the Royal Society of London for the Improvement of Natural Knowledge, each Fellow was explicitly to be a “Gentleman, free, and unconfin’d.”18 Hooke’s need to make a living disqualified him from fellowship, though his talent made him indispensable. The solution—he was appointed to the salaried position of curator of experiments for the Royal Society in 1662—made him the first scientist in British history19 to receive a salary, though the salary in question was long in coming. It took until 1665,20 when Hooke was appointed professor of geometry at Gresham College at an annual stipend of £50 for life; the Royal Society then coughed up another £30, to make good on their original promise to Hooke of £80 a year.
Robert Hooke’s pioneer status makes him a persuasive bridge between technology and science, which was in 1665—and for decades thereafter, in Britain and everywhere else—still the province of amateurs. Hooke spent his life in an occasionally successful search for both recognition and recompense, attempting, among other things, to turn his Law of Elasticity into ownership of the watch escapement, whose spring-loaded movement was a direct outgrowth of the Law.* When he died, his frugally appointed apartments contained a considerable amount of cash, largely earned from his surveying, contributing to a probably false reputation as a bit of a miser, but his attitude toward invention seems to be, in its way, as significant an innovation as his vacuum pump.
While Boyle is traditionally remembered as the more important transitional figure in the development of steam power, he exhibited a strong prejudice in favor of those whose experiments were entirely in service of the search for truth, as opposed to those “mere Empiricks”21 and “vulgar chemists” simply trying to “produce effects.” This distinction makes his position clear in the never-ending debate between pure and applied science—really, between science and invention—that was already thousands of years old by Boyle’s day.
The debate continues into our own day. Which is why it is Robert Hooke’s life, rather than Boyle’s, that leads from Torricelli (whose promising start on the potential uses of vacuum were forestalled by conservative Aristotelianism) and von Guericke (whose undoubted talent for innovation is mostly remembered as a circus act) on the path to engine 42B, and to Rocket.
The next steps on that path would take the technology of steam and vacuum irrevocably into the world of commerce.
* Part of the story of the Magdeburg hemispheres remains a bit of a mystery. Even if Gericke had been able to achieve a perfect vacuum—unlikely, with the equipment he had at hand—the total air pressure at sea level on a globe twenty inches in diameter would be a bit less than five thousand pounds—a lot, but not too much for thirty horses.
* Though it should be noted that in 1676, the French physicist and priest Edmé Mariotte independently discovered “Boyle’s” law, and that in many European countries, the same equation is known as Mariotte’s Law.
* Tellingly, in order to keep his discovery secret, and so secure his status as its discoverer, he first published the Law in the form of an anagram.