The Philosophical Breakfast Club (20 page)

Nebulae—from the Latin word for “little mists” or clouds—are viewed as filmy, diffuse areas in the night sky. The Milky Way (the galaxy in which the earth is located) appears even to the naked eye as a hazy band of white light arching across the entire celestial sphere. With his extremely powerful telescope, William Herschel had found the heavens swarming with such systems. Following the astronomer and mathematician Johann Heinrich Lambert and the philosopher Immanuel Kant, Herschel had thought of these as “island universes,” what we would call galaxies—glorious systems of millions of suns and stars and planets. Herschel told the author Fanny Burney, in 1786, that these “universes … might well outvie our Milky Way in grandeur.” The filmy matter viewed through the telescope he thought was simply the millions of separate bodies, so far away that they could not be resolved into single points or disks. But Herschel later changed his mind, coming to believe that the filmy matter was a real gaseous matter, a kind of “shining fluid” of unknown properties—a conclusion supported in 1864, when William Huggins used the recently invented spectroscope (which contained a prism to disperse the light from celestial objects into its component parts) and found that some nebulae exhibited a spectrum characteristic of a gaseous body rather than a group of stars and planets.
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In the process of studying his father’s nebulae, John Herschel discovered more than five hundred never before seen. At that time John believed that his father’s original view was correct: nebulae were made up of individual stars, not any real nebulous matter (he later came to accept the real existence of gaseous nebular matter). His catalog of the positions of over 2,300 nebulae was presented to the Royal Society in 1833, and won Herschel much acclaim as well as the gold medals of both the Royal Society and the Astronomical Society.
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But it was arduous work. He was frustrated and exhausted: “Two stars last night, and sat up till two waiting for them. Ditto the night before. Sick of star-gazing—mean to break the telescope and melt the mirrors,” he complained at one point.
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Herschel was spending his days in London, at his rented house down the street from Babbage’s place, and his nights at the telescope in Slough. The strain was beginning to show to others; even his aunt Caroline, who had gone back to her original home in Hanover after her brother died, was worried, telling John she wished she had stayed in England to look after him.
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Caroline begged him to get married: “Pray, think of it, and do not wait till you are old and cross.”
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She felt that, at thirty-four years of age, he had waited long enough. His friend James Grahame predicted that if Herschel did not marry soon he would end up a crotchety and eccentric scholar. Grahame took action: he introduced Herschel to Mrs. Alexander Stewart, widow of a Scottish Presbyterian minister, who lived in London with her two daughters and six sons. Herschel was smitten with one of the daughters, Margaret, called “Maggie,” a lovely and vivacious young woman of eighteen, a little more than half his age. She would later be described by Maria Edgeworth as “such a delightful person, with so much simplicity and so much sense.”
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Babbage, his confidant in his other two love affairs, told him approvingly, “You have now chosen one whom all who know her say is worthy of your affections.”
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Whewell told Jones, “I think Herschel is now going to be married in good earnest!”
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Herschel invited Whewell to come to London for the wedding and asked him to be a trustee of the marriage settlement (perhaps recalling how Babbage had botched the job during his first engagement).

On their honeymoon, Herschel and Margaret passed through Birmingham, where they hoped to visit Matthew Boulton’s manufactory at Soho. They were eager to observe the pioneering assembly-line production of what were then called “toys”—buckles, buttons, and small metal boxes. Boulton, overwhelmed by visitors, was unable to accommodate them, and they were forced to visit other local factories instead.
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Strange as it may seem to us, it was not unusual to spend part of a honeymoon in this way. The educated classes had begun to visit the new, great factories in droves, amazed at the spectacle of huge steam-powered machines being worked by hundreds of men, women, and children. It became so fashionable that, as the Herschels found, factory owners had to turn visitors away by the score.

After the honeymoon, his energy and happiness restored, Herschel began to work on a book that would introduce Bacon’s method to the broader reading public, influencing the young Charles Darwin and
countless other men of science: his
Preliminary Discourse on the Study of Natural Philosophy
. The flamboyant publisher and science popularizer Dionysius Lardner (who had changed his name from the rather more pedestrian Denis) had asked Herschel to write a book for his new series, the Cabinet Cyclopedia, in which he intended to publish books on each of the major scientific fields. Herschel’s book would serve as the introductory volume of the series, explaining proper scientific method to a general audience. Coleridge’s “Preliminary Treatise on Method” had played the same role for the
Encyclopaedia Metropolitana
when it appeared in 1818. Herschel jumped at the opportunity. (Lardner also asked Whewell to write the volume on political economy for his series, but Whewell demurred—he did not wish to steal the limelight from Jones’s forthcoming work.)
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Herschel’s book sported the image of a bust of Bacon on the title page, and a quote from
Novum Organum
on its frontispiece. Herschel praised Bacon as the “great reformer” of science, exhorting men of science to follow his inductive method. Agreeing with Bacon that the natural philosopher should not be like the philosophical spider, inventing theories out of his own imagination, Herschel proclaimed that the natural philosopher seeks “causes recognized as having a real existence in nature, and not being mere hypotheses or figments of the mind.”
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Herschel illustrated this point with a timely example—the discovery of fossils of shellfish on mountaintops, which had been discussed by Charles Lyell in his
Principles of Geology
earlier that year. What could have caused those remains of scallop and mussel shells to end up on the top of a mountain? Some savants had suggested that these fossils were produced by a “plasticity” of the soil, or by the influence of the celestial bodies. Herschel mocked those views as being mere “figments of fancy”: there was no reason to think that the soil was “plastic,” whatever that meant, or that the sun, moon, stars, or planets could cause fossils to appear on earth.

It was more scientific to look at known causes to explain new phenomena, Herschel explained. It was already known, Herschel reminded his readers, that the relative level of sea and land had changed over time. Lyell’s book had depicted on its frontispiece an engraving of the Temple of Serapis in Pozzuoli, Italy. This Roman temple had been above sea level when first built, and was above sea level now, but its columns showed evidence of having been partially submerged at some point in the past: there was obvious water damage and erosion. This proved, Lyell had argued,
that very gradual processes of shifting land and water—so gradual that the temple was not destroyed—could be responsible for great changes over time. Whewell would soon give the name “uniformitarianism” to Lyell’s view that the natural processes operating in the past were the same as those that could be observed at work in the present, and were, for the most part, slow-acting.
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Herschel concluded that the most likely cause for the appearance of fossil shells on the mountaintops was “the life and death of real mollusca at the bottom of the sea, and a subsequent alteration of the relative level of land and sea.” These fossils were evidence that the mountaintops had once been submerged under the water, and had risen up slowly over eons of geological time. This suggestion that the earth was much older than previously thought was precisely what the opponents of Lyell’s theory—who Whewell dubbed the “catastrophists”—were trying to avoid. As they realized, once you accepted that there were immense stretches of time in which incremental geological changes could occur, you were forced to admit that there was enough time to bring about incremental biological changes as well. Reading Lyell’s book, in fact, was instrumental in Darwin’s realization that evolution was a very real possibility.

Throughout the book, Herschel gave many examples of the application of Bacon’s inductive rules by men of science, drawing upon his own experience in astronomy, chemistry, and optics, as well as upon the scientific researches of his friends.

One of Bacon’s rules, as outlined in his
Novum Organum
, counseled the natural philosopher to seek out “crucial instances” or crucial experiments that could definitively decide between two rival theories. An example given by Bacon, and discussed by Herschel, was a way to decide whether the tendency of heavy bodies to fall downward was a result of some mechanism in the bodies themselves, or (as Newton would later argue) the attraction of the earth. Bacon had noted that if the attraction of the earth was the cause of the downward movement of bodies, then it followed that the closer a body was to the center of the earth, the stronger the force and velocity of its downward approach. Bacon suggested that this question could be answered definitively by the use of two clocks—one run by “leaden weights,” one by a spring. After setting them to the same time, one clock would be positioned at the top of a high building, such as a church steeple, and one placed into a mine dug deep into the earth. If the clocks began to diverge in timekeeping,
it would be clear that the weight of the clock in the mine was being attracted more forcefully than the weight of the clock on the church steeple, and thus that there was a force of attraction between objects and the center of the earth.

As Herschel pointed out proudly in his discussion in the
Preliminary Discourse
, his friends Whewell and Airy had recently carried out this crucial experiment. Their motive was not to test the truth of Newton’s law of universal gravitation, which had long been enthusiastically accepted by the scientific community. Rather, Airy and Whewell used Bacon’s experiment as a way to measure the mean density of the earth. The difference between the gravitational force exerted at various distances from the center of the earth would depend on the density of the earth, because of its relation to mass (density is mass divided by volume), a key variable in Newton’s gravitation equation. Knowing the density of the earth would allow astronomers like Herschel to calculate the densities of the sun, moon, and other planets.

At the end of the eighteenth century, Henry Cavendish—the discoverer of hydrogen, which he called “inflammable air”—using a brilliant apparatus he had devised with the aid of the geologist John Michell, had calculated that the density of the earth was 5.48 times the density of water, incredibly close to the value accepted today: 5.52 times.
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In his paper describing the experiment, published in the Royal Society
Transactions
, Cavendish suggested that new experiments be conducted, with different types of instruments, in order to test whether some error due to his complex apparatus had corrupted his result.
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Airy and Whewell were the first to try to obtain an independent value for the density of the earth.

In 1826, Airy and Whewell borrowed two pendulums from the Royal Society and brought them to the Dolcoath copper mine, known as the “Queen of the Cornish mines”—one of the deepest mines in Cornwall, a county pockmarked with them. They hoped to compare the vibration of a pendulum at the surface of the earth with the vibration of the same pendulum deep in the mine, at a depth of 1,200 feet below the surface. The difference in their rate of vibration would disclose the difference in the force of gravity at the two places, and thus allow them to calculate the density of the earth.

Much to the amusement of the local miners, Whewell and Airy spent several weeks climbing up and down ladders placed in the mine, alternating positions between the two pendulum stations. In a pamphlet Whewell
published later, he complained that “the daily fatigue of the observers in descending and ascending … was not slight, as may easily be imagined when it is considered that it was the same process as clambering by ladders down and up a well 3½ times the height of the pinnacle of St. Paul’s; and this was accompanied by a stay of 6 to 8 hours at the bottom of the mine amid damp and dirt.”
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He admitted to his friend Lady Malcolm, in a letter written from the bottom of the mine, that “I have a barrel of porter close to my elbow,” which presumably helped the time pass more quickly, but may have impeded the ascent up the ladder at the end of the shift.
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The experiments came to an abrupt halt when one of the pendulums was dropped as it was being hauled up to the surface in a protective box lined with dry reeds: some smoldering candle wick had fallen on the packing material and burned through the ropes. Two summers later Whewell and Airy tried again, only to find that one of the pendulums was faulty. Nevertheless, Herschel praised Airy and Whewell for their attempts, in the process reminding his readers that although not every experiment was successful, the man of science must persist in going out in the field to conduct them.
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Herschel did more than promote Bacon’s inductive view of scientific method in the book. He also sanctioned Bacon’s emphasis on the practical benefits of scientific knowledge, what Bacon had called the
deductio ad praxim
. Herschel praised science for the refinements it had introduced into such industries as smelting, bleaching, soap-boiling, and sugar production. He pointed approvingly to the discoveries that had led to methods for treating and preventing illness: iodine for curing gout, lemon juice for the prevention of scurvy, quinine for fever. And he congratulated Humphry Davy for his invention of the safety lamp, which enabled miners “to walk with light and security while surrounded with an atmosphere more explosive than gunpowder.” The unnamed inventor of a mask worn by needle makers to protect their lungs from the minute particles of steel and stone that surrounded them also merited a mention.
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Herschel reminded his readers of the importance of accurate lunar distances, praising the scientific and mathematical skill that allowed those calculations to be made at all (he left the reader to draw his or her own conclusion as to the likely benefits of having the figures calculated by a machine).
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