by Sarah Dry
He returned to Britain to become Astronomer Royal for Scotland at the age of twenty-seven. It was a precocious appointment, but he soon realized that the grandest thing about the post was the title. He had scant funds, and the observatory was chronically understaffed. The skies of Edinburgh were smeared with hazy coal smoke, layered over with low cloud, gray as the stones on the houses of New Town. It was hard to see anything like what he had seen in the Cape. Nevertheless, he set himself to fulfilling the demands of his office.
His moment of inspiration arrived at the same time as a wife. He decided to embark upon a journey to Tenerife, to see if he could bring precision instruments to the top of the mountain and establish an observatory there. No longer precocious, by this time Piazzi Smyth was thirty-six, and his bride, Jessie, a surprising forty. They married on Christmas 1855, and by the following June they were sailing to Tenerife. In the hold of an expensive yacht that transported them were the following instruments: an actinometer, magnetometer, thermometers, electrometers, spectrum apparatus, and polarimeter, loaned by none other than the Astronomer Royal, George Airy. Barometers and more thermometers were loaned by Admiral FitzRoy, head of the Met Office. The hydrographer loaned him four chronometers. And Robert Stephenson trumped them all by lending him an entire yacht, the RMS Titania, with a crew of sixteen men for the return journey.
It was a classic voyage of imperial reckoning, made possible by the well-engineered tools of the industrial revolution, the instruments he’d been loaned by the greatest scientists of the day, the expensive sailing ship, and the well-trained crew he had the run of. What Piazzi Smyth was doing was attempting to verify an old hypothesis with an enviable pedigree. Isaac Newton had proposed in his Opticks of 1704 that astronomical observations would be greatly improved by removing the “injurious portion of the atmosphere.” Since then, many had concurred but no one had attempted to prove the point. Tenerife was closer to London than the Cape, and so more convenient, but it also presented potentially insurmountable obstacles to scientific observation. It was possible that the instruments would prove impossible to transport to the peak, fail to operate once there, or that perpetual cloud would surround the summit. If, on the other hand, those obstacles could be overcome, then more science and more scientific vision could be had.
FIG. 3.2. The crew of the Titania en route to Tenerife, photographed by Charles Piazzi Smyth in 1856. Credit: Royal Observatory Edinburgh.
The mountain could be a machine for making facts out of theories, as Piazzi Smyth put it. And so, by implication, could the astronomer himself. But doing so required balancing between worlds in a manner that brought to mind a man teetering atop a peak. A Scot who had been born in Naples, trained in southern Africa, and professionally employed in Edinburgh (a proud capital that was simultaneously an outpost of London), Piazzi Smyth was a creature of the periphery. As such, Piazzi Smyth was uniquely qualified to make the attempt.
His success depended on maintaining the standards of metropolitan astronomical science on a mountaintop several thousand miles from Britain. His own excitement, and the appetite for exploration it fed, had brought him first to the Cape and now to Tenerife. It was a necessary precondition for an explorer-scientist in the middle decades of the nineteenth century. But the spirit of exploration sometimes sat uneasily with the sort of self-restraint insisted upon by the men who stayed in London. For while the requests of the London scientists who had loaned him the instruments (and given him the money) were many, and varied, they were also quite firm—even rigid—about the extent of the domain to which they felt Piazzi Smyth had earned access. Even on an expedition designed to go further, astronomically speaking, than had ever been gone before, it was possible to go too far. That went for the types of observations Piazzi Smyth could make—geology and biology were not welcomed—and it also went for the forms of expression Piazzi Smyth used to describe his discoveries. Piazzi Smyth knew this, and this knowledge helps explain the defensive note that crept into his writing about the moment of first contact between him and the mountain. He knew that he had to suppress his own emotional response in favor of the instrumental readings he’d been empowered to make. If he worked hard and got lucky, he might manage to render the mountain a suitable outpost for British astronomy, a new sort of colony: a temporary, provisional, but potentially bounteous source of new knowledge. This goes some way toward explaining Piazzi Smyth’s curious locution and defensive recounting of his dramatic arrival at Tenerife. He was trying to abide simultaneously by two norms for watching the skies—the one based on emotion, the other on what he called “physical explanation.” What is interesting about Piazzi Smyth is not only that he felt himself to be caught between—or spread across—these two ways of looking at clouds, but that he shared the experience of a doubled response with his readers.
The need to eliminate the personal from scientific observation took on a special urgency in the case of mid-nineteenth-century astronomy, when it became apparent that differences in the reaction times of observers could become a significant source of error when it came to making extremely precise observations of celestial movements. There was a phrase for this problem, the “personal equation,” which suggested the desirability of reducing human differences to a numerical factor, a handicap that could then be subtracted from the results, giving a true number. Astronomers became professionally paranoid, on guard against any and every source of error. “Vigilance can never sleep; patience can never tire,” wrote one popular writer at the end of the century. “Variable as well as constant sources of error must be anxiously heeded; one infinitesimal inaccuracy must be weighed against another; all the forces and vicissitudes of nature—frosts, dews, winds, the interchanges of heat, the disturbing effects of gravity, the shiverings of the air, the tremors of the earth, the weight and vital warmth of the observer’s own body, nay, the rate at which his brain receives and transmits its impressions, must all enter his calculations and be sifted out from his results.”6
Even taking such extreme precautions, it was impossible to eliminate personal differences between observers—specifically, the reaction times that varied between observers trying to determine with extreme accuracy the time at which a star crossed a certain location in the sky. The more precisely astronomers were able to map the stars, the more the personal equation mattered, since small differences in the reaction times of observers made a big difference when tiny units of time were being measured. One way around this problem was to establish hierarchies of observers, each of whom was himself observed by the managers of observatories, men such as George Airy, head of the Royal Observatory at Greenwich.7 Piazzi Smyth was not alone on the mountaintop, but from the perspective of astronomers like Airy, he might as well have been. There was no one to watch Piazzi Smyth, no one against whose observations his own could be checked, no one observing him making his observations.
When Piazzi Smyth mentioned that for most people, looking up at a sublime bit of meteorology—the shifting of clouds to reveal a monumental peak—was an emotional experience, he was, in a somewhat oblique way, making reference to a perennial astronomical bugbear. Though astronomers used the term personal equation in hopes of eliminating differences between observers, Piazzi Smyth was here drawing attention to the ineffability of personal observation, to the way it could not be reduced to numbers. By rendering the subjectivity of the observer into a commonplace to be acknowledged rather than a troublesome anomaly to be eliminated, Piazzi Smyth was suggesting the possibility that scientists could be simultaneously objective and subjective, impersonal and personal.
If the problem of precision was significant in astronomy, it was partly because the astronomy that Piazzi Smyth and most of his contemporaries were doing was, above all, a cartographic exercise. The vast energies and expenditure poured into astronomy in the first decades of the nineteenth century by the French and the British were a form of scientific colonization. Nearly a century after Newton had shown it was possible to predic
t the motions of heavenly bodies according to a set of physical laws, astronomers were mostly still preoccupied with working out what this meant in practice. Mapping the position of the stars, the sun, the moon, and the planets—called positional astronomy—was a continuation of the research program that Newton had first set out in 1687 with the first edition of his Principia. For this, long hours of observation, with the most precise instruments, used by the best-trained observers overseen by the most demanding supervisors, were necessary to produce a map sufficiently refined to demonstrate both the theoretical potential of the Newtonian system and, just as important, to wring from it the practical benefits of improvements in navigation and surveying. Knowing the heavens made it possible, in a direct and practical way, for nations to know the earth, and in knowing the earth, to control an ever-greater part of it.8 It also made it possible to predict with extraordinary accuracy the movements of celestial objects, an accomplishment which brought considerable prestige to the discipline of astronomy and served as a beacon for the ambitions of many other physical sciences.
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As powerful a tool as positional astronomy could be, astronomers always hoped for more. Piazzi Smyth had come of age in the 1830s, when astronomers felt increasingly emboldened to hope that it might be possible to say not only where but also what the stars were. Once astronomers saw the prospect of moving beyond celestial mechanics—once seen as the ultimate “perfect” system—an exciting but newly confounding world opened up before them. Newton’s cosmos had been sterile—a clean clockwork universe in which God made intermittent appearances to keep the planets on their eternal orbits but little else occurred. The new cosmos was filled with energy that bombarded the planet, bathing it in a relentlessly dynamic flux of light and magnetism. The smooth and singular orbits predicted by Newton’s mathematics were replaced by complex and messy traces of thousands of barometers, thermometers, magnetometers, and a host of other instruments that sought to catch the cosmic fluxes of the universe.
There was no more influential proponent of the idea that nature could be made to yield her secret laws than Alexander von Humboldt, the Prussian explorer and naturalist. When he stopped at Tenerife, he laid his anchor in mist “so thick, that we could scarcely distinguish objects at a few cables’ distance.” Like Piazzi Smyth, he feared that the mountain would remain out of sight, but “at the moment we began to salute the place, the fog was instantly dispelled. The Peak of Teyde appeared in a break above the clouds, and the first rays of the sun, which had not yet risen on us, illuminated the summit of the volcano.”9 Despite the mist, Humboldt noted the effects of the transparency of the atmosphere, “one of the chief causes of the beauty of the landscape under the torrid zone.” Not only did it heighten colors, harmonizing and contrasting them, but it changed the very “moral sensibilities” of the inhabitants of southern realms, leaving them with a “lucid clearness in the conceptions, a serenity of mind, correspond[ing] with the transparency of the atmosphere.”10 Clear skies, then, could lead to clear minds.
Humboldt never stopped thinking about both how natural environments affected human beings and how humans could understand the physical nature of those environments. Decades later, as he sat down to write a book that was the culmination of a lifetime of travel and contemplation, he returned to the question of how different landscapes affect people differently, or the “different degrees of enjoyment presented to us in the contemplation of nature.” Thinking back on the many places he’d been, a few leapt out. In addition to the “deep valleys of the Cordilleras,” where tall palms had created a forest above the forest, he returned once again to Tenerife, remembering
when a horizontal layer of clouds, dazzling in whiteness, has separated the cone of cinders from the plain below, and suddenly the ascending current pierces the cloudy veil, so that the eye of the traveler may range from the brink of the crater, along the vine-clad slopes of Orotava, to the orange gardens and banana groves that skirt the shore.
What was it that gave scenes like these the ability to move a man’s heart, to spark the “creative powers of [a man’s] imagination”? Part of their potency lay in their changing aspects, in the way moving clouds or water dramatized the flux of forces that was ever present but not always so visible. Humboldt called this the “peculiar physiognomy and conformation of the land, the features of the landscape, the ever varying outline of the clouds, and their blending with the horizon of the sea.” The result of all this change was that he, like Tyndall, had the eerie sense that nature was imbued with emotion—his own emotion. “Impressions change with the varying movements of the mind,” wrote Humboldt, “and we are led by a happy illusion to believe that we receive from the external world that with which we have ourselves invested in it.”11
FIG. 3.3. Alexander von Humboldt, painted by Julius Schrader in 1859, with Mount Chimborazo and Mount Cotopaxi in the background.
This happy illusion was in large part due to the unity of Nature. “The powerful effect exercised by Nature springs, as it were,” wrote Humboldt, “from the connection and unity of the impressions and emotions produced.” Unity was the feature that caught the attention. To achieve true understanding, it was necessary to go deeper. As humankind developed intellectually, it became possible to move beyond the primordial feelings of unity and arrive at an even more powerful method for apprehending the world.
By degrees, as man, after having passed through the different gradations of intellectual development, arrives at the free enjoyment of the regulating power of reflection, and learns by gradual progress, as it were, to separate the world of ideas from that of sensations, he no longer rests satisfied merely with a vague presentiment of the harmonious unity of natural forces; thought begins to fulfill its noble mission; and observation, aided by reason, endeavors to trace phenomena to the causes from which they spring. [emphasis added]12
By separating thought and emotion, Humboldt thought it would eventually be possible to disentangle the many threads of differing phenomena—magnetic, astronomical, and meteorological—and assign them to their respective origins, or, in other words, “to trace phenomena to the causes from which they spring.” Only by regulating emotion could mankind surpass the powerful first impression of unity. Humboldt’s vision was both gradual and bold. It would take time, but in the end a much deeper understanding of the multiple forces of nature at work could be achieved. The way to turn “mere” natural history into a physics of the earth (Physik der Erde) was to “track the great and constant laws of nature manifested in the rapid flux of phenomena, and to trace the reciprocal interaction, the struggle, as it were, of the divided physical forces.”13 Taken together, these readings would reveal the true and truly singular face of the earth.14
Just as it became increasingly possible and attractive to determine the effect of physical forces on earth, so it became almost irresistible to look for the invisible but powerful threads that linked the earth and the heavens. Humboldt did not distinguish between the forces present on earth and those that prevailed throughout the universe. His approach encompassed nothing less than the entire cosmos. The “harmonious unity of nature” necessarily knit together the heavens and the earth. In the same way, it constituted a sort of undulating tapestry of physical forces that could be discerned in the isolines of temperature and pressure, and in the corresponding bio-geographical continuities that Humboldt so painstakingly reconstructed.
Humboldt’s vision was shared by John Herschel, the son of the great astronomer William Herschel, discoverer of Uranus, and himself an accomplished scientist. John Herschel helped organize the so-called Magnetic Crusade of the 1830s, an ambitious attempt to simultaneously map changes in the earth’s magnetic field at different places around the globe.15 The results of this multi-year expedition were stunning, revealing that Earth’s magnetic field changed in response to that of the eleven-year cycle of sunspots. No better example of Humboldt’s belief that beneath flux lay order could have been hop
ed for. Here was a powerful justification both for the gathering of multiple sorts of data—on sunspots, solar spectra, gravity, radiation, and much besides—and for the effort needed to disaggregate those phenomena from each other. Knowledge, in this sense, would be as much subtractive as additive. To understand both the emotional power of a place like Tenerife, and the physical phenomena made manifest, required tools for working backwards from the powerful impression of unity to the underlying causes which together operated to create the traces recorded by the many instruments Piazzi Smyth took with him to the island.
For Piazzi Smyth and his peers, separating the effects of the terrestrial atmosphere from that of the solar atmosphere was a prerequisite for understanding the true nature of either. In this sense, it was not possible to do solar physics without doing terrestrial physics or vice versa. This new physical way of doing astronomy firmly knit together the earth and the cosmos, to create, as one writer put it, “a science by which the nature of the stars can be studied upon the earth, and the nature of the earth can be made better known by study of the stars—a science, in a word, which is, or aims at being, one and universal, even as Nature—the visible reflection of the invisible highest Unity—is one and universal.”16
Earth’s atmosphere played a peculiar role in this search for unity. In its shifting movements, the atmosphere and the clouds which floated in it represented the difficulty of seeing to the essence of things, as well as the need to always be vigilant about the objective of observation. Clouds were sometimes obstructions to the visions that lay beyond—of stars, of peaks. But they were also aspects of the natural world and therefore worthy of study in themselves. They represented a particular variety of the fullness of nature, the way in which the veils that she drew across herself were themselves part of nature. The objects that obscure vision are themselves worth looking at. In this way, the atmosphere was a doubled object, both an impediment to science and an object of it.