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A NA COFFI N When Johann Joachim Becher was born in 1635 to a Lutheran minister, the Thirty Years War had been rag- ing for eight years. Though the chaotic conditions in Germany prevented Becher from getting much of an education, they posed no obstacle to his advancement. When Becher was 26, the elec- tor of Mainz appointed him to be his expert on the management of local industry. Becher also managed to get himself appointed profes- sor of medicine at the University of Mainz. Although he had no for- mal medical training, he had recently been given a degree in medi- cine as a we(l(ling present. Becher subsequently foun(1 employment in the courts of the elector of Bavaria and the emperor of Austria, and in 1673 he turned up in Holland with a plan for making sand into gold. The Dutch were skeptical, but Becher gave a dramatic demonstration to a government- appointe(1 commission and persua(le(1 them to approve the sand project. According to him, large quantities of silver were needled to produce the gold, so this was duly provided. Becher soon left HolIan(l, claiming later that intrigue against him 90
A NAIL FOR THE COFFIN 91 had made him fear for his life. It is uncertain how much of the Dutch government's silver he took with him. In any case, he sailed to England, where he represented himself as an expert on mining. At one point, Prince Rupert, a nephew of Charles I, sent Becher to the mines in Scotland. The sailing of Becher's ship was held up by storms for four weeks, and he used his enforced leisure to write a book titled Foolish Wisdom and Wise Fol/l/y. In this work, Becher told the story of his life, incorporating outlandish stories along the way. He wrote of a stone that could make people invisible, of a flask that contained words, and of geese that lived in trees and hatched eggs with their feet. In 1667 Becher published another book, Physica Subterranea, in which he expoun(le(1 a theory that was to profoun(lly affect chemistry for more than a century. In the book Becher accepted only two of the traditional four elements, earth and water. He then divided earth into three types, so that in effect there were still four elements. He named the three kinds of earth terra llapida, terra pinguis, an(1 terra mercurial/is. The second of these, which he described as an "oily earth," was suppose(1 to be present in all combustible substances an(1 was release(1 when those substances burned. This looks like yet another alchemical theory, and of course that is exactly what it is. It is little more than a variation on the three- principle theory of Paracelsus. However, in the hands of Becher's pupil, the German physician Georg Ernst Stahl, it became something more. Stahl wrote a number of books between 1703 an(1 1731 in which he elaborated on Becher's idea. Renaming Becher's terra pinguis "phlogiston" (after the Greek phl/ogios meaning "fiery"), Stahl wrote at great length about its role in combustion and in the calcination~ (oxidation) of metals. According to Stahl, these were essentially the Oxygen had not yet been discovered at this time. Thus, to avoid confu- sion, I use this eighteenth-century term and also the corresponding term "calx" for the oxide of a metal.
92 THE LAST SORCERERS same process; both took place when phlogiston was released into the air. And when caIxes were heated with charcoal, which was supposedly rich in phlogiston, the metals could be obtained again. The idea seemed so plausible that European chemists soon gen- erally accepted the phlogiston theory. To be sure, there were some difficulties. When wood was burned, its phlogiston escaped into the air, and the ashes weighed less than the original wood. But caIxes weighed more than the original metal. It appeared that the release of phlogiston led to weight loss in one case and weight gain in the other. This apparent contradiction seems not to have bothered Stahl. He simply didn't discuss the problem in his books. Other chemists explained the weight gain by postulating that particles of fire were incorporated into a metal when a caIx was formed. Yet others sug- geste(1 that there were two kin(ls of phlogiston, one with weight, the other with the property of"levity." When the phlogiston containing levity was released, the substance that had contained it became heavier. Some chemists even denied that there was any weight gain. Eighteenth-century chemistry was primarily a matter of observing chemical changes, and measurements were often crude. Furthermore, the chemists of the time commonly used large burning lenses, which were capable of producing high temperatures. If a lens vaporized some of the metal or caIx on which it was trained, a decrease in weight might in(lee(1 be observed after calcination. No one had ever isolated phlogiston, and this hypothetical sub- stance apparently behaved in a contradictory manner. Nevertheless, an incorrect theory was quickly accepted, because what chemistry (lesperately nee(le(1 then was a theory that could be used to gui(le research. The phlogiston theory, as we shall see performed this func- tion a(lmirably. ~ 1 A more nearly correct theory of calcination and combustion had been proposed in the previous century. In 1630 the Frenchman Jean Rey theorized that the weight increase during calcination came about because air was incorporated into the caIx. However, by the time the phlogiston theory was proposed, Rey's idea had been forgotten. It
A NAIL FOR THE COFFIN 93 didn't fit in with the prevailing idea that fire broke substances down into their components. And of course the phlogiston theory did. HENRY CAVE ND I OH Henry Cavendish was descended from the dukes of Devonshire on one side and from the dukes of Kent on the other. His father, Lord Charles Cavendish, was either the third or the fifth son of the second duke of Devonshire. His mother, Lady Anne Grey, was the daughter of Henry, duke of Kent. She was not in robust health when she married, and she died when Henry was only two years old. Henry was born in 1731. Little is known about his childhood, but in 1749 he matriculated at Cambridge University, though nothing is known of his course of study there. However, it must have included mathematics, because he exhibited great mathematical expertise in later life. He remained in Cambridge until 1753, when he left without taking a degree. The reason for this is unknown, but it has been sug- gested that he might have had scruples about the religious test that was required of degree candidates, who were required to assert that they were bona fide members of the Church of England. During his adult life, Cavendish never attended any church, and he never identi- fied with any religious sect. Henry's younger brother, Frederick, entered Cambridge two years after Henry and also left without taking a degree. After Frederick's studies were completed, the two brothers set off on a grand tour of the continent. It is not known how long they remained or what places they visited. However, there is one story about their trip through Europe. While staying at a French inn they walked by an open door and looking in, saw a corpse laid out for burial. Neither of the Cavendish brothers said anything until the next day, when Frederick asked, "Brother, slid you see the corpse?""Brother, I Lid," Henry replie(l. Nothing more was said about the matter. After returning to England, Henry lived with his father until Lord CharIes's death in 1783. His father was not well off for a man of his
94 THE LAST SORCERERS position and gave Henry an allowance that was quite small by the standards of the day. After being elected to the Royal Society in 1760, Henry dined regularly at the Royal Society Club. His father provided him with five shillings a day for dinner, never anything more. Lord Charles Cavendish might not have been wealthy, but he was a natural philosopher and experienced experimentalist. Indeed his research on heat, electricity, and magnetism earned him praise from Benjamin Franklin. Henry must have learned a lot from his father, because he, too, became a meticulous experimenter. Some of Henry's experiments in physics and most of his chemical experiments were performed while he was still living under his father's roof At the age of 40, Henry inherited a fortune of more than a million pounds, though it is not known which of his relatives the money came from. Although he was now one of the richest men in England, he spent little on himself The clothing he wore consisted of frayed family hand-me-downs of the style ofthe previous century. Cavendish didn't entertain, and his dinner each night consisted of a leg of mutton- and nothing else. However, he permitted himself one luxury: he acquired a large scientific library. Once, when the library was in a state of disorder, Cavendish hired a man who was in difficult financial circumstances to classify and catalog the books. Sometime later, after the job was com- pleted, one of Cavendish's acquaintances mentioned that the librarian was still finding it difficult to make ends meet and hinted that Cavendish might want to help. Without asking how much was needed, Cavendish wrote out a check for £10,000, a small fortune at the time. He could be generous in other ways, too. When asked for chari- table contributions, he invariably tried to find out what the largest contribution was and then equaled it. According to another story, he once attended the christening of a relative and, learning that it was customary to make a gift to the chil(l's nurse, gave her a han(lful of gold guineas without bothering to count them first. Though wealthy, Caven(lish was inherent to money. He was the largest holder of bank stock in England, and cash accumulated rapidly
A NAIL FOR THE COFFIN 95 in his bank account. One day his banker came to visit and informed Cavendish that he had a balance of £80,000 in his account. Cavendish answered that he did not want to be "plagued" about it, and that if it was any trouble, he would withdraw the money. The banker assured him that this would not be necessary and suggested that some of the money should be invested. "Do so," Cavendish replied,"and don't come back here to plague me about it, or I will remove it." After receiving his inheritance, he acquired a house in CIapham, on the outskirts of London, where he lived as a recluse, filling the house with scientific equipment. Cavendish had a high squeaky voice and a stutter, and he avoided speaking to people whenever he could. Throughout his life he was terrified of women, and he sometimes covered his eyes and fled when he encountered them in the street. Nevertheless, he regularly attended meetings of the Royal Society. His devotion to science was total. He seems not to have said much at the meetings, however. As his fellow scientist Lord Brougham observed, Cavendish"probably uttered fewer words in the course of his life than any man who ever lived to fourscore years, not at all excepting the monks of La Trappe." Because Cavendish was so reclusive, many of the important details about his life remain unknown, and his biographers have generally focused on his scientific work. However, there are numerous stories about his eccentricities. For example, he avoided conversation with his housekeeper and communicated with her by leaving notes. Once when he was at the home of Joseph Banks, president of the Royal Society, a foreign visitor appeared. He had come to Lon(lon expressly to meet Caven(lish, whom he consi(lere(1 to be one of the greatest natural philosophers of his time. At his first opportunity, Cavendish fled and had himself driven home in his carriage. Cavendish died on February 24, 1810. The several accounts of his last hours are similar, but differ in certain details. According to one story, when he realized that he was dying, he rang for his valet and gave him the following instructions: "Min(1 what I say, I am going to die. When I am dead, but not before then, go to Lord George
96 THE LAST SORCERERS Cavendish and tell him of the event. Go!" Half an hour later Cavendish summoned the servant again and had him repeat the instructions. When the valet returned to the bedroom for the third time, Cavendish was dead. According to a second account, when Cavendish's servant dis- covered that his master was dying, he rushed to the house of Sir Everard Home, a well-known physician. Home accompanied the servant to CIapham, where he found Cavendish dying. When he saw Home, Cavendish raged at the servant, saying that at his age any attempts to postpone (leash would only prolong his miseries. Home nevertheless remained throughout the night, and Cavendish died (luring the early morning hours. . According to a third story, when Cavendish was dying, he instructed his servant to leave him alone and not to return until a certain later time, when he expected to be dead. However, the servant, who was anxious about his master's condition, returned before the specified time to look in on the dying man. Cavendish, who was still conscious, angrily ordered him out of the room. When the servant returned at the time that his master had stated, Cavendish was dead. In his will, Cavendish left none of his money to science. Most likely he believed that, because the money had come from his family, it should go back to the family. The famous Cavendish laboratory at Cambridge was founded on the bequest of a relative 61 years after Henry Caven(lish's (leash. He was buried in All Saint's Church in Derby, now Derby Cathedral, but there is no plaque in the cathedral to indicate his interment there. Most likely Cavendish would have been pleased to know that he was to be as anonymous in death as he was reclusive in life. THE "D I $COVERY" OF PHLOG I $TON In 1766 the Royal Society published Cavendish's Three Papers ContainingExperiments on Factitious Air, describing his experiments with hydrogen, which is produced when metals are dissolved in acids.
A NAIL FOR THE COFFIN 97 Hydrogen had previously been observe(1 by Boyle and by Caven(lish's contemporary Joseph Priestley. However, Cavendish is credited with the discovery of the gas because he was the first to perform experi- ments for the purpose of determining its properties. His name for hydrogen was "inflammable air." However, he had no doubt that this gas he had discovered was phlogiston. In science, theory often determines what we observe. Cavendish was simply interpreting his results in terms of the accepted theory of his day. He was far from the only scientist who did so. For example, when Priestley discovered oxygen, he named it"dephIogistated air." Cavendish began his studies of the properties of hydrogen by mixing it with air and bringing about an explosion. He soon con- cluded that"this air, like other inflammable substances, cannot burn without the assistance of common air." He also (letermine(1 that air was 20.8 percent oxygen, which is remarkably close to the modern figure of 20.9 percent. Next, he performed experiments to determine the density of the hydrogen and concluded that the gas was "5490 times lighter than water or near 7 lighter than common air." He then performe(1 some further, more accurate experiments and corrected these figures to 8,760 and 11, respectively. The modern figure for the latter is 14.4. However, Caven(lish's apparatus was quite cru(le by modern standards, and he must have conducted the experiments very carefully to get so close. Caven(lish's papers next (lescribe(1 experiments with carbon dioxide, which he called "fixed air." He studied its solubility in water and its efficacy in extinguishing flames. He conclu(le(1 that when one part carbon dioxide was mixed with eight parts of ordinary air, candles would not burn. He also determined the density of carbon dioxide, finding that it was about 50 percent heavier than air. This result is astonishingly close to the modern value of 52 percent. I will pass over the other experiments described in these papers except to say that they were numerous. Cavendish's next paper on chemistry was of much greater interest. Published in 1784 under the title Experiments on Air, it described his discovery that water could be
98 THE LAST SORCERERS made by combining hydrogen and oxygen. After Priestley discovered "dephlogisticated air" (oxygen), Cavendish began to experiment with the gas. In one celebrated experiment he mixed air and hydrogen in a long glass cylinder and caused the hydrogen to burn. He found that the water that condensed in the cylinder had no taste or smell and that no sediment was formed when it was evaporated. He had produced pure water. This was followed by experiments in which hydrogen and oxygen were mixed in a large glass globe and exploded with an electric spark. Again, water was produced. Cavendish also obtained quantitative results, finding that water was a combination of two volumes of hydrogen and one volume of oxygen. Cavendish didn't realize that he had shown that water was a com- pound of hydrogen and oxygen and therefore not an element. He was hobbled by the phlogiston theory, the only theory that chemistry then had. He concluded that hydrogen was water saturated with phlogiston and that oxygen was water from which all the phlogiston was re- moved. When they were combined, of course water was produced. Though his conclusions were erroneous, Cavendish had performed a crucial experiment that put another small nail into the coffin of the still widely accepted four-element theory. Although he misinterpreted his results, he had performed one of the crucial experiments in the history of chemistry. WEIC;HINC; THE EARTH Cavendish's most famous experiment, performed when he was nearly 70, is often described as "weighing the Earth." This description is a little misleading, because what he was actually trying to do was deter- mine the Earth's density. In order to do this, he needed to calculate the Earth's mass, though that wasn't his primary goal. Before Cavendish's experiment, no one knew the strength of the force of gravity.* This might sound a little surprising at first, but not Perhaps I should add, for the benefit of readers who know a little phys- ics, that Cavendish wanted to measure Newton's gravitational constant.
A NAIL FOR THE COFFIN 99 when you consider that the attraction the Earth exerts on terrestrial objects depends on two things: the mass of the Earth and the intrin- sic strength of the force of gravity. If the Earth had twice the mass that it does and gravity were half as strong, we would all have exactly the same weight. Conversely, if the Earth were half as dense and grav- ity twice as strong, the weight of terrestrial objects would also be un- changed. In order to make this measurement, Cavendish used an appara- tus known as a torsion balance, which consists of a light rod to which two lead balls are attached, one at either end. The rod is suspended on a long slender wire, and two larger and heavier lead balls are placed in stationary positions near the ends of the rod. Knowing that the gravitational attraction between the lead bans was extremely small, Cavendish knew that he had to eliminate any effects, such as air cur- rents, that might interfere with his measurements. So he placed the apparatus in a mahogany case and took some a(l(litional precautions, which he (lescribe(1 as follows: "I resolve(1 to place the apparatus in a room which would remain constantly shut, and to observe the motion of the arm tthe rod to which the smaller bass had been attached] from without by means of a telescope: and to suspend the leaden weights in such manner, that I could move them without entering the room." If a slight horizontal motion were imparted to the balls, then there would be two forces acting on the rod: the gravitational attraction between the smaller and heavier balls, and a force that was (lue to the twisting of the wire. These two forces would cause the balls to swing back and forth horizontally in a manner that somewhat resembled the motion of a pendulum. By observing the motion of the rod, Cavendish was able to calculate the tiny gravitational attraction between the bans on the rod and the larger stationary ones. From this he could determine what the intrinsic strength of the force of gravity was, and once he knew this, he could calculate the mass of the Earth and its (lensity. Cavendish repeated the experiment 29 times and found that the Earth weighed 6 x 102 (6 followed by 21 zeros) metric tons. The
100 THE LAST SORCERERS average density of the Earth was 5.48 times greater than that of water. This was a great improvement on the best previous result (obtained by a different method) of 4.5, and it was better than any determina- tion of the Earth's density that was made before the twentieth century. Cavendish's result diners from the modern figure of 5.52 by less than 1 percent. It is much better than a result of 5.67 that was obtained in 1841 from an experiment that was repeated, not 29, but more than 2,000 times. When Cavendish died, his contemporary and biographer George Wilson wrote that"he did not love; he did not hate; he did not hope; he did not fear." Wilson also described Cavendish as consisting of"an intellectual head thinking, a pair of wonderfully acute eyes observing, and a pair of very skillful han(ls experimenting or recording." And of course the latter assessment is correct. Cavendish was the greatest experimental scientist of the eighteenth century. JOSEPH PRIE$TI~EY Joseph Priestley, who was born in 1733, in Fieldhead in the county of Yorkshire, was the son of a dresser, a craftsman who treated woolen cloth to give it an even texture. Toseph's father, Jonas, was a Calvinist dissenter. In those days a dissenter was anyone in England who belonged to a religious denomination other than the Anglican Church. Dissenters included Roman Catholics, Jews, and Quakers as well as dissenting Protestants. Technically, being a dissenter was illegal; there were still laws that specified punishments for anyone who did not subscribe to the Thirty-nine Articles of the Church of England. The laws against Roman Catholicism were especially harsh. The saying of mass by a foreigner was a felony; and if an English priest said mass, he was committing high treason. But these laws, which ha(1 been enacted in the previous century, were not enforced. Priestley lived with his parents until he was four years old. He was then sent to live with his grandfather, who had a farm a few miles away, and remained there until his mother died in childbirth in 1739.
A NAIL FOR THE COFFIN 101 When he was nine, he was sent to live with his father's older sister and her husband. Priestley's aunt saw to his education, sending him to several different local schools. In 1746 he contracted a serious illness, probably tuberculosis. Cared for by his aunt, he slowly recovered, although he remained in frail health for several years. At the age of 15 he left the school he had been attending and began to learn Hebrew at a school operated by a dis- senting minister. Finally, in 1752 he enrolled in a dissenting academy in Daventry in Northhamptonshire. At the time it was necessary to be an Anglican to attend universities like Oxford and Cambridge, so the dissenting academies were created to serve the needs of non-Anglican students. These academies provided the best education available in England at the time. Because they were not hobbled by tradition, they were more progressive than the old English universities. While he was in Daventry, Priestley decided to prepare for the ministry. He had previously studied French, German, Italian, and Hebrew and now began studying Greek. He also began to write manu- scripts that were later published as books. He wrote in shorthand, so that he could write them quite rapidly. It was sometimes said later that he could write books faster than other people could read them. In 1775 Priestley left Daventry to become an assistant minister in a church in Needham Market, Suffolk. By this time, he had repudi- ated Calvinism and was developing theological ideas of his own, some of them quite unorthodox by the stan(lar(ls of the (lay. Later, he would describe himself as a "furious freethinker" during this period of his life. This might not have caused any problems if he had not chosen to give a series of lectures based on the material he had written in Daventry. But give them he did, with the result that his congregation (lwin(lle(1 consi(lerably. In turn, this re(luce(1 his income, which had not been very large to begin with. Hoping to supplement it, he an- nounced that he would open a school. This idea ended in utter fail- ure. He (li(ln't get a single pupil, which was har(lly very surprising, considering the reputation he had gained in the local community. Priestley left Nee(lham in 1758 to become minister to a congre-
102 THE LAST SORCERERS gation in Nantwich in Cheshire. Again he decided to supplement his income by opening a school. This time he was more successful and soon had 36 pupils. Until then he read scientific books but couldn't perform experiments, because he couldn't afford apparatus. But now, although his teaching duties prevented him from doing much scien- tific work, his income was enough to buy some scientific instruments. He simply didn't have the time to minister to a congregation, teach, and perform experiments too. I,ONDON In December 1765 Priestley journeyed to London, hoping to make the acquaintance of some of his fellow British scientists. By this time, he had attained some prominence as the author of a number of text- books that were based on the courses he taught at his school. While in London, he performed his first experiments, some of them under the direction of Benjamin Franklin, who was in London at the time as a representative of the government of Pennsylvania. Priestley continued experimenting, and soon he had written a manuscript titled The History and Present State of Ellectricity, with Original/ Experiments. In Tune of 1766 he was elected to the Royal Society, and his book on electricity was published in 1767. At this time, his experiments were primarily in physics. He had not yet developed the great interest in chemistry that was eventually to lead him to some very significant discoveries. I~EED~ In 1767 he accepted a cad to become minister to a congregation in Lee(ls. During his six years there, he published voluminously on theo- logical, political, and scientific topics. His publications ranged from pamphlets on a variety of topics to three-volume works. By now, Priestley had been a Unitarian for some time, and his theological and political works often became quite controversial. He spoke, for ex-
A NAIL FOR THE COFFIN 103 ample, of the "idolatrous worship of Jesus Christ." Priestley believed that Tesus had been only a man, and he did not hesitate to say so. His political opinions, too, were quite radical by the standards of the day. He believed, for example, that under certain circumstances revolution was justified, and he attacked the intolerance that made all religious denominations except the Anglican Church illegal. "Let all the friends of liberty and human nature join to free the minds of men from the shackles of narrow and impolitic laws," he wrote, going on to say, "Let us free ourselves, and leave the blessings of freedom to our posterity." Such ideas wouldn't sound very inflammatory today. How- ever, voicing them in eighteenth-century England was a different matter. His ideas were attacked by the archdeacon of Winchester and by the jurist William Blackstone. Priestley answered both men and soon found himself the center of controversy. He did not neglect science while he was in Leeds, but continued performing electrical experiments, as well as studies of light and of optical and astronomical instruments. His writings on these subjects brought an invitation from Captain Tames Cook to join Cook's second voyage as the expedition's astronomer. Priestley accepted but some clergymen on the Board of Longitude, which was sponsoring the voyage, blocked his appointment. Opposition to his ideas was wide- spread at this time. King George III expressed his disapproval of Priestley, and so did many people of lesser rank. It was around this time that Priestley discovered soda water. "Fixed air" (carbon dioxide) had long been known to chemists, and Priestley had experimented with it a little. One day he had the idea of trying to dissolve the carbon dioxide in water. He succeeded and found that the water fizzed. Priestley gave some of the soda water to friends and then went on to other kinds of research. Some years later the British Navy expressed interest in the use of Priestley's sparkling water as a remedy for scurvy, but naturally it was unsuccessful. How- ever, soda water quickly became popular in other circles, even earning praise from Lord Byron, who wrote the following stanza on the back of the manuscript of his poem Don Juan:
104 THE LAST SORCERERS I would to Heaven that I were so much clay, As I am blood, bone, marrow, passion feeling- Because at least the past were passed away, And for the future (but I write this reeling, Having got (trunk excee(lingly to (lay, So that I seem to stand upon the ceiling) I say the future is a serious matter- And so for God's sake hock and soda-water! THE DI$COVERYOF OXYClEN In 1772 Priestley published an account of five years of experiments with "airs" (gases). The work he described was so important that it immediately established him as one of the great chemists of the day. While he was in Leeds, Priestley discovered three gaseous oxides of nitrogen, inclu(ling nitrous oxide ("laughing gas") an(1 hydrogen chloride gas. Before he began his experiments, chemists had known of only three gases: hydrogen, carbon dioxide, and air. He continued his experiments and discovered even more new gases: sulfur dioxide, silicon fluoride, ammonia gas, and nitrogen. However, his most important (liscovery was oxygen. In June 1774 Priestley got a burning lens with a (liameter of 12 inches an(1 imme- diately began to experiment with it. In one experiment he turned the lens on mercury caIx (mercuric oxide) and obtained an"air" in which candles burned more brightly than they did in ordinary air. At first he did not know what to make of this result, so he continued experi- menting. He soon foun(1 that he coul(1 get the same gas from certain other materials, such as lead oxide. To fin(1 out what this "air" was, he performe(1 further experi- ments. He (li(1 tests to see if it resemble(1 nitrous oxide. It (li(ln't. Still puzzled, Priestley turned to other work, including his experiments with sulfur dioxide, and then he had an idea. If nitrous oxide was mixed with air, the quantity of air was diminished (because another
A NAIL FOR THE COFFIN 105 oxide of nitrogen was formed, using up some of the oxygen). He tried mixing the nitrous oxide with his new air and found that it was also diminished. Furthermore, the decrease was greater than that which he observed when he mixed nitrous oxide and ordinary air together. Next, Priestley took a mouse and put it in a container full of the new air, expecting it to live for about 15 minutes. Instead, it was still alive after half an hour. Apparently this gas had something in common with ordinary air, with the difference that it was somehow "better." Priestley continued experimenting, and even he tried breathing some of the oxygen himself. He found that the feeling of breathing it was not much different from that of breathing ordinary air. However, he wrote, "I fancied that my breast felt particularly light and easy for some time afterwards." Priestley called the substance he had discovered "dephIogisticated air." According to the theory of the (lay, air was necessary for combustion because there had to be something that would take up the phlogiston that the burning object released. If objects burned better in the new"air," then this meant that it was air (levoi(1 of phlogiston. Ordinary air did contain phlogiston, and this caused com- bustion to proceed more slowly. Similarly, nitrogen, with which Priestley also experimented, was "phIogisticated" air. The large quan- tities of phlogiston that it contained prevented it from supporting combustion. PRIE$TI,EY'$ PATRONS Priestley wasn't wealthy like Boyle and Caven(lish so he (li(ln't have the leisure to spend as much time on scientific experiments as they did. However, by this time his fame had grown and he soon had a patron. William Petty, the second ear] of Shelburne, admired Priestley's scientific work and offere(1 him a post supervising the education of his two sons and collecting material on subjects under discussion in parliament. The salary was to be two and a half times what he was then earning, and Shelburne also provided his new
106 THE LAST SORCERERS employee with a townhouse near the earl's London residence and a house on his estate in Wiltshire. Priestley took up the post in 1773. When he left it in 1780, Shelburne continued to pay him half the £300 salary he had been receiving, and other patrons contributed smaller amounts to make up the difference. One of the patrons found him a house on the outskirts of Birmingham, where he could live comfortably and devote himself to scientific experimentation. Priestley set up a scientific laboratory in the house. While he lived there some of his patrons died or stopped contributing, but there were always others willing to take their places. Dr. Erasmus Darwin and the pottery designer and manufacturer Tosiah Wedgwood, the two grandfathers of Charles Darwin, were among those who contributed to his support. Priestley did not live in Birmingham in utter tranquility. After the French Revolution began in 1789, many people in England began to fear that there might be attempts at revolution there, too. Some believed that Priestley, who had published writings expressing sympathy with the French republicans, might try to foment it. He was attacked by the press and denounced in the House of Commons. In 1791 rioters burned down his house and destroyed his laboratory, some (listance from the house. He found a new house and began to construct a new laboratory. However conditions in England were rapidly becoming intolerable. When the French executed Louis XVI in 1793, the hysteria increased further. By now some of Priestley's scientific colleagues were snubbing him, and his friends were urging him to leave Englan(l, saying that it wouldn't be safe to remain. Priestley took their advice, and in 1794 he and his wife sailed to America. By now Priestley was famous, and he got a warm welcome in the young republic. After he settled at NorthumberIan(l, in Pennsylvania, the trustees of the University of Pennsylvania voted unanimously to offer him the chair of chemistry. But Priestley declined the offer. By the summer of 1795 he had set up yet another laboratory and was again busy writing and performing experiments. But then, in 1797,
A NAIL FOR THE COFFIN 107 attacks against him began to appear in the press, just as they had in England. The press had been somewhat hostile since his arrival in America and now the attacks intensified. Priestley was characterized as an enemy of religion and of law and order. Priestley had never commented on American politics, but this was conveniently ignored. One journalist even attacked Benjamin Franklin, who had died at the beginning of the decade, because Franklin had been one of Priestley's friends. Although Priestley was often attacked in print, he never had to fear for his life or his property in America, as he had in England. At one point, he contemplated emigrating to France, but soon gave up the idea. He spent the remaining years of his life living in NorthumberIan(l, writing, experimenting, and sen(ling papers to the American Philosophical Society. He also arranged for the publication of religious works that had been written years before and left unpub- lished for various reasons. Priestley's History of the Corruptions of Christianitywas published in 1797, and his Index to the Bible appeared a few months after his death in 1803.
