Davy told his audiences at the Royal Institution that the voltaic pile was nothing less than “a key which promises to lay open some of the most mysterious recesses of nature.”4 He made good on that promise by using the pile to run electrical current through samples of soda and fused potash, thereby discovering the new elements sodium and potassium. Davy convinced enough people of the power of the pile that he managed to raise £1,000 by subscription for building a gigantic battery—composed of two thousand pairs of plates, each eight inches square—in the basement of the Royal Institution. Eventually, Davy discovered more elements—calcium, boron, and barium—and proved that “oxymuriatic acid” was not a compound but rather an element, which he called “chlorine.”5
Other men of science were studying the properties of light—diffusion, reflection, refraction, polarization—trying to determine its elemental nature. Was light made up of tiny particles subject to Newtonian laws of gravity, as Newton himself had thought, or was it made up of waves traveling through an undetectable medium pervading the universe, known as the “luminiferous ether”? In a lecture to the Royal Society, Thomas Young described an ingenious experiment meant to answer this question.
Young had sent a beam of sunlight from one end of his laboratory to the other, deflected by a mirror through a tiny hole punched into a window shutter. He held a thin card edgewise into the sunbeam, so that it cut the beam of light into two parts, one passing on each side of the card. These two beams of light were projected onto the wall. Young observed alternating “fringes” of dark and light areas. When he prevented the beam on one side of the card from passing, by blocking it with a screen, the fringes disappeared, and there was only one bright spot on the wall.
Young realized that the result was something like what happens when two stones are thrown into a pond next to each other: the water waves ripple out from each stone in a circular pattern, the waves of each circle crossing into the path of the other. Sound waves were known to act this way, rippling out from their source, crossing into or “interfering” with other sound waves, causing an intermittent pattern of loud and soft tones. Young concluded that light, like sound, must be made up of waves. When the two beams of light were projected together on the wall, the interference pattern of the waves caused the fringed arrangement of bright and dark areas.6
Not everyone was convinced. Other theorists were performing experiments in which light appeared to have the properties of particles. Today we know that this is because light has both particle and wave properties. In the nineteenth century, this unsettled state of affairs led to a flurry of optical experiments and mountains of scientific papers arguing one side or the other.
Although he was spending most of his time in his chemical laboratory, Herschel was ostensibly in London to study law. After taking top honors in the Tripos examinations of 1813, and having the honor of being one of the youngest men ever named a fellow of the Royal Society later that year, Herschel had angered his father by deciding to enter the legal profession.7 His father had hoped he would become a clergyman. William Herschel had not been motivated by any particular religious piety in urging this course to his son, but he saw that a position as a country curate would provide security, some financial independence, and, most of all, time: time to engage in scientific pursuits. As a clergyman, John would have the leisure to conduct experiments, collect fossils, study minerals. It was a tried-and-true career path for many men of science in those days when there was no graduate education in science, and no scientific careers to pursue, besides the few professorships that paid little, if anything—not enough even to pay for the equipment required to perform experiments. John refused point-blank to follow this path. The two argued bitterly, but John was steadfast. He moved to London and entered his name on the rolls of Lincoln’s Inn.
We can empathize with William Herschel. The law seems an odd choice, after all, for one who had resolved to “leave this world wiser than he found it.” But John was taking to heart Bacon’s injunction to make the world a better place, and felt that the law would give him a platform for carrying out that mission. It was also, as it is today, a good way to make a living. As he wryly wrote his friend John Whittaker, “I do not think that you ever imagined me serious in my threats to take this step, but so it is.… God send quarrels among the good people of this nation, and pour forth the bitter vials of litigation like water on every side … so that we lawyers may never want work—Amen.”8 At the same time, however, Herschel was setting up his laboratory. The attraction to chemistry was too strong to be resisted.
Like most newcomers to the field, Herschel first tried reproducing the experiments of others. In his 1810 work Elements of Chemistry, the Scottish chemist Thomas Thomson had announced the discovery of “muriatic sulphur”—a liquid composed of sulfur, oxygen, and muriatic acid (hydrochloric acid), formed when sulfur combined with oxygenated hydrochloride gas. Over a series of days in March 1814, during a visit back to Cambridge, Herschel tried to produce muriatic sulfur in a laboratory he had set up in the room of a friend. He enlisted Babbage, who was still a student with a laboratory of his own, and the two of them went back and forth between their two rooms, trying to produce this strange fluid in their flasks. Years later, in an article on the absorption of light in colored substances, Herschel would refer to his experience of the “muriated liquor of Dr. Thomson,” and describe its dramatically changeable appearance—“yellowish-green in small thicknesses, and bright red in considerable ones.” But the two novice chemists were unable to reproduce Thomson’s results.
Herschel was more successful in replicating the results John Dalton had attained when he precipitated silicate of potash (potassium carbonate) by acids. Dalton had determined that the precipitate was glass, not silica as others had argued. Herschel found that with high enough heat the precipitate did fuse “into a glass, not very perfect, but transparent at the edges.”9 Dalton and Herschel were right. Indeed, by adding lime (calcium oxide) to this recipe, one could produce the famed Bohemian glass, prized for its hardness and clarity, and typically fashioned into the lovely multicolored etched goblets and decanters that were beginning to be displayed in the homes of the well-to-do.
Herschel was soon reporting to Babbage his discovery of a “new acid”—hyposulfurous acid.10 He found a curious, though seemingly insignificant, result: that hyposulphite of soda (known today as sodium thiosulfate) had the property of dissolving silver salts rapidly and completely. Years later, Herschel’s memory of these experiments would lead him to be one of the pioneers in the invention of photography; it would provide a method of protecting the image produced by light rays on a layer of silver salts from destruction by the further action of light.11
Experiments on the crystalline structure of bicarbonate of potash led Herschel to studies of the optical properties of crystals. “This salt has the most remarkable optical structure of any chrystal I have yet examined, and presents phenomena of quite a new kind,” Herschel crowed in his notebook. Herschel used highly polished crystals of this substance to begin experiments on the diffusion and refraction of light, and thus entered into the optical fray. Soon crystals of quartz, apophyllite, Iceland spar (crystallized calcium carbonate), and tourmaline—in all the colors of the rainbow—were sent to Herschel from colleagues around the world, forming a glowing and glittering collection that would have been envied by mineralogists and jewelers alike. This collection became the toolkit for Herschel’s ongoing work on optics.
Tourmaline—a gemstone that occurs in nature in blue, red, yellow, green, brown, and all the shades in between—was a particular favorite of men of science of the time. It had the astonishing property of becoming electrically charged after heating and cooling, with a positive charge at one end and a negative charge at the other. This is known as “pyro-electricity” (from the Greek word pyr, meaning fire). Tourmaline also becomes charged under high pressure, the polarity changing when the pressure is reduced, causing the crystal to oscillate. Using two polished plates of t
ourmaline, Herschel found that if the crystal axes of the two plates were perpendicular to each other, a polarized ray transmitted by the first plate did not penetrate the second. From this experiment Herschel drew important conclusions about the relation between the crystalline structure of a transparent substance and its optical properties, conclusions that suggested to Herschel that the wave theory of light was true.12
Herschel also studied the beautifully iridescent mother-of-pearl, the inner lining of mollusk shells built up from thin layers of a calcium carbonate crystal. Recalling Thomas Young’s discovery of the interference of light waves, Herschel proposed that the iridescence of mother-of-pearl was caused by interference. He suggested that the thickness of a layer of calcium carbonate in mother-of-pearl is about equal to the length of a wavelength of visible light. Because of this, as light bounces off the successive layers, waves interfere with others, causing the shimmering interplay of bright and dark areas we experience when observing mother-of-pearl. Herschel was right about this explanation, and was tantalizingly close in his calculations.13
As he was conducting these colorful experiments, Herschel sent letter after letter to Whewell describing his optical results, which he was also transcribing in his small, elegant handwriting into his experimental notebooks and publishing in the pages of the Transactions of the Royal Society. Whewell, still at Cambridge, was susceptible to the pull of chemistry and optics, describing Herschel with some envy as “untwisting light like whipcord, cross-examining every ray that passes within half a mile,” and assuring him that he would soon discover some new optical laws.14 Whewell was inspired to begin his own experiments with crystals. He wrote a paper showing how to calculate the angles between the edges and faces of the crystals of fluorspar, or calcium fluoride.
Whewell probably used the dramatic purple-blue specimens of fluorspar known as “Blue John,” which came from a famous mine in Derbyshire. Blue John was chosen by Matthew Boulton of Birmingham as the base for his highly sought-after ormolu ornaments in the late 1700s: bronze casts in decorative shapes were fused to a smooth background of the purple-blue stone, whose deep translucent color made the bronze shine like gold. Whewell’s more scientific use of this lovely mineral led him to write a second paper, in which he outlined a general method for calculating angles made by any planes of crystals, using three-dimensional geometry. It also fostered a lifelong interest in the study of minerals, which would lead him to seek the professorship of Mineralogy as soon as it became available, in 1825.
Herschel often urged Babbage to come visit, bringing whatever chemicals he happened to have at hand so the two of them could experiment together. Although after graduating Babbage was spending much of his time writing and publishing mathematical papers, he admitted that visiting Herschel had revived his “chemico-mania.”15 Babbage and Herschel spent a summer together in Devonshire “mineralizing,” collecting unusual crystals to use in experiments. Herschel mocked Babbage for piling onto several horses loads of a mineral Babbage took to be a rare compound, only to find under chemical analysis that it was common carbonate of lime.
Whenever they were both in London, Herschel and Babbage went together to witness the experimental demonstrations of William Hyde Wollaston (brother of the Jacksonian Professor at Cambridge), who had become fabulously wealthy by discovering and patenting the process by which platinum was made malleable. Although he could afford vast quantities of chemicals, Wollaston used only the most minute amounts of substances in his experiments. It was remarked with some awe that his entire chemistry set could fit on a tea tray.16 Some said that he had unusual, even supernatural, sense organs, with which he could detect the effects of analysis on such small amounts of matter. Babbage more phlegmatically believed that Wollaston had particularly well-developed powers of concentration, which he focused with intense precision on every object being studied.17 Babbage and Herschel resolved to be more like Wollaston in their own experiments.
Later, Herschel and Babbage replicated and extended experiments that had been conducted by the French savant Dominique François Jean Arago. They set a thin disk of copper in rapid rotation below a magnetized needle hanging upon a silk thread. When the disk was not moving, there was no discernible magnetic force between the disk and the needle. But when the disk began to spin, the needle deviated from its position, and finally was dragged around with the rotation of the disk. Next they “reversed the experiment.” Herschel and Babbage mounted a powerful horseshoe magnet, capable of lifting twenty pounds, to a rotating lathe, and placed a circular disk of copper over it, suspended on a silk thread. As soon as the magnet was set in motion, the disk began to rotate.
The men replaced the copper disk with plates of different metals: zinc, tin, lead, antimony. They found that the best conductors of electricity made the plates that most activated the magnetic force.18 Some years later Faraday would show the significance of this fact by demonstrating that these magnetic phenomena were the result of induced electrical currents, further establishing a connection between electricity and magnetism.
Jones, too, would soon be experimenting, although not in a laboratory like Babbage, Herschel, and Whewell. After graduating, and attaining a position as a country curate, Jones used his small vicarage garden to teach himself the rudiments of agriculture, starting from the chemistry of the soil, as Davy had outlined in his 1813 work Elements of Agricultural Chemistry. Jones may have carried out Davy’s recommendations for soil analysis, involving evaporation, titration, and precipitation, and the careful weighing of the products of these processes—processes that would require, Davy advised, a sensitive balance, a sieve, an Angland lamp, a collection of glass tubes and dishes, Hessian crucibles, porcelain evaporating basins, filter paper, a Wedgwood mortar and pestle, and “an apparatus for collecting and measuring aeriform fluids.”19 Jones became esteemed by his parish for his understanding of agricultural techniques. He used his knowledge to grow prize-winning roses. He became an avid beekeeper, carefully observing the social interactions of the hive and applying his findings to understand how humans acted in groups. He told Whewell that his bees were as good as Herschel’s optical instruments as a means for coming to scientific knowledge.20 It was a kind of human chemistry, and would one day help Jones in his great project of reforming economics.
AFTER A YEAR in London it became clear that Herschel could not continue the charade of studying the law, when he was in fact working full-time on his scientific pursuits. He had tried to do it all, admitting to Babbage “how ardently I wish I had ten lives, or that capacity, that enviable capacity of husbanding every atom of time, which some possess, and which enables them to do ten times as much in one life.”21 But he was exhausted. Herschel sought relief in an academic post, applying for the newly vacant professorship of Chemistry at Cambridge; he lost by only one vote.22 After spending some weeks in the summer of 1815 at the seaside resort of Brighton to recover his strength, Herschel decided to accept an offer made to him some months earlier by one of his former teachers at St. John’s: to return to Cambridge as a sub-tutor and examiner in mathematics. Although not as prestigious (or well paid) as a professorship, it at least offered the chance for an academic career and, better yet, a return to Whewell and Jones—Babbage had recently graduated.23
But Herschel quickly realized he was not made for teaching. Soon after arriving in the fall of 1815 he described his routine to Babbage: “You are pretty well aware what a job it must be to be set from 8 to 10 to 12 hours a day examining 60 or 70 blockheads, not one in ten of whom knows anything but what is in the book.… In a word, I am grown fat, full and stupid. Pupillizing has done this.”24 By the summer of 1816, Herschel decided to leave Cambridge for good, and help his aging father, who had recently been created a Knight of the Guelphic Order, becoming Sir William Herschel. No longer could Sir William or Caroline spend long nights at the telescope, but important parts of the elder Herschel’s life work were still incomplete. Herschel spent the summer with his father in Dawlish, a popular re
sort on the Devonshire coast. It was a particularly cool and gray season in England, because of the eruption of Mount Tambora in the Dutch East Indies the year before; the weather reflected the somber mood of John as he made his life-changing choice. At the end of the summer, John agreed to become his father’s assistant.
Leaving Cambridge was hard for Herschel to do, however much he hated his tutoring duties. He told Babbage, “I shall go to Cambridge on Monday where I mean to stay just time enough to pay my bills, pack up my books, and bid a long—perhaps a last farewell to the University.… I always used to abuse Cambridge as you well know with very little mercy or measure, but, upon my soul, now that I am about to leave it, my heart dies within me.”25
Herschel embarked upon his career in astronomy. First he had to learn the basics—how to grind and polish telescope mirrors, how to observe with a telescope, and how to carry out his father’s special method for sweeping the sky to look for double stars. William Herschel had listed over eight hundred double stars in several major star catalogs, in a number of cases proving that they must be binary stars—physically related pairs orbiting around common centers of gravity, not merely unrelated pairs seen by accident in the same direction in the sky. These binary systems generated great scientific interest, because they showed that Newton’s law of gravitation—which accounts for the planetary orbits in our solar system—held beyond our solar system and thus was a truly universal law. John Herschel’s first work in astronomy consisted in studying these double stars, trying to detect any changes that might have taken place in the positions of the components of the binary systems since his father’s observations in the early part of the century. He used these differences as the basis for determining the orbital periods of the systems. Later, he and his new friend Sir James South would produce a catalog of 380 double stars, an impressive achievement that would win them the Gold Medal of the Astronomical Society and the Lalande Prize of the Royal Academy of Sciences in Paris.26
The Philosophical Breakfast Club Page 7
