The Philosophical Breakfast Club (9 page)

Lavoisier published his new system in a monumental work, the
Traité Élémentaire de Chimie
(
Elements of Chemistry
), which appeared in Paris in 1789, the year of the storming of the Bastille, marking the start of the French Revolution, and the year of America’s ratification of its constitution. This revolutionary work set the foundation for modern chemistry. It spelled out the influence of heat on chemical reactions, in the new non-phlogistic theory of combustion. It described the nature of gases and the reactions of acids and bases to form salts. It proclaimed, for the first time, the Law of Conservation of Matter: that in chemical reactions, matter changes its state, but not its quantity: matter cannot be destroyed, or created out of nothing. The book depicted in great detail the new and expensive apparatus Lavoisier had designed for his chemical experiments, illustrating them with thirteen exquisite engravings drawn by Lavoisier’s talented young wife, Marie-Ann Pierrette Paulze.

Within a few years of publishing his treatise, Lavoisier fell victim to the revolutionary fervor in France, losing his head to the guillotine during the Reign of Terror in 1794. But Lavoisier had the satisfaction of recognizing, a few years before his death, that he had been successful in igniting a “revolution … in chemistry.”

Now, in the first quarter of the nineteenth century, electricity was all the rage, and studies of it were part of a chemist’s repertoire. Ever since Luigi Galvani had ghoulishly made the legs of a dead frog dance by applying a metallic couple to connect nerve and muscle in the 1780s, “electricians” sought to understand this strange force. In 1800, Alessandro Volta
had built the first electrical battery, known as the voltaic pile, by piling up several pairs of alternating copper and zinc disks separated by cardboard soaked in brine. When the top and bottom disks were connected by a wire, an electric current flowed through the voltaic pile and the connecting wire.

Volta’s description of the pile in the pages of the Royal Society’s
Transactions
sparked work on electricity by English chemists, including Humphry Davy. Davy was a close friend of Coleridge, with whom he discussed both poetry and science. A precocious lad, he began to study science seriously when apprenticed to a surgeon. This led to his being offered a position in charge of the laboratory of the Bristol “Pneumatic Institute,” which was formed to investigate the medicinal uses of airs and gases. Not long afterwards, Davy was hired as one of the first lecturers at the Royal Institution, and was soon regaling crowds of five hundred or more at a time with his demonstrations—sometimes involving the self-application of nitrous oxide gas (now known as “laughing gas”), to which Davy would become addicted. So many flocked to Davy’s lectures that Albemarle Street, where the Royal Institution was located, became London’s first one-way street to try to ease the congestion of carriages. After attending Davy’s lectures, Faraday sent him a three-hundred-page book of notes he had taken, so impressing the older man that Davy hired Faraday as his assistant and occasional valet. Faraday would soon become director of the laboratory at the Royal Institution, and later the first of its chemistry professors.
³

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 tourmaline, 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.