Ever since its publication in 1830–31, John Herschel’s Preliminary Discourse on the Study of Natural Philosophy has been recognized as epoch-making and canonical. It is rather surprising, therefore, that to date there exists little to no consensus on any aspect of the book, not even on what it is really about. This chapter provides a brief overview of the available literature on Herschel’s Preliminary Discourse. In doing so, it attempts to both improve upon and go beyond current Herschel scholarship.

Despite John Herschel’s extensive work in the fields of chemistry, optics, geology, mineralogy, and the philosophy of science, it was primarily as an astronomer that he was recognized during his lifetime and remembered after his death. Herschel’s astronomical endeavors can be summarized as establishing and extending the astronomical projects of his father William Herschel (1738–1822) and his aunt Caroline Herschel (1750–1848). By establishing, Herschel brought an observational and mathematical rigor to his father’s observations that transformed them from the results of an individual with unique instrumentation to data useful and accessible to the wider astronomical community. By extending, Herschel continued the observational program of his father and aunt, revisiting his father’s observations, updating his catalogs of double stars, nebulae, and star clusters, and extending the Herschelian project to the skies of the southern hemisphere. Yet the observational aims and methods of William and Caroline Herschel were markedly different from the astronomy being pursued by most other astronomers during their lifetimes. To understand John Herschel’s long astronomical career and influence, an overview of the scope and aims of the dominant form of astronomy during this period is needed that can provide the background to the work of his father and aunt and the context of his own.

John Herschel’s destiny lay in science. Ahead was a career of creation in astronomy, botany, chemistry, geography, meteorology, photography, and much else. Not least would be the attention he paid to mathematics. His royal road to becoming a leader in Victorian science was paved by William and Caroline Herschel, his celebrated father and aunt, both of whom were acknowledged authorities in astronomy. William, a German émigré to England, held the position of ‘King’s Astronomer’ and in this role established a rapport with George III, an amateur astronomer himself. William gained wider recognition as the discoverer of ‘The Georgian’ (known later as the planet Uranus) and Caroline as the discoverer of comets.

As early as 1826, John Herschel wrote, “astronomers are seldom draftsmen, and have hitherto … contented themselves with very general and hasty sketches.”1 This was more than a passing complaint with past depictions of astronomical objects. It was an exhortation to a generation of astronomers to begin taking draftsmanship seriously. With its increasing focus on the physical features of astronomical bodies like the Sun, the planets, comets, and the Moon, as well as the intricate physical complexities of the Milky Way, celestial nebulae, and clusters of stars, the astronomy of the nineteenth century demanded a new and systematic focus on draftsmanship as a means of observation. In this way, astronomy was very much in line with other observational sciences of the period like geology and minerology, botany and zoology, archaeology and ethnography, all of which required, alongside detailed descriptions, more exact pictures of their respective subject matter.2 As the act of drawing became embedded into routine scientific recordkeeping practices, it also became closely tied to what counted as proper scientific observation. Herschel was not just in tune with these important developments, he exemplified them in his own observational performances. This is evinced by his exquisite skills and techniques in drawing in the service of science and, above all, astronomy. Herschel’s observational practices were embodied in a set of visualizing instruments, techniques, and materials. What follows is a survey of some of these practices as they range over a lifetime of carefully observing and drawing many sorts of phenomena.

The Preliminary Discourse on the Study of Natural Philosophy, which Herschel published in Dionysius Lardner’s Cabinet Cyclopaedia series in 1830, can be a difficult book to interpret.1 As commentators have emphasized, its content and the circumstances of its publication indicate it is perhaps better understood not (or at least, not merely) as a technical treatise on scientific inference and methodology but rather in the tradition of “conduct manuals,” a popular genre that offered readers insight into how they might elevate and refine their character.2 The Preliminary Discourse invokes not just prescriptions for scientific practice but also the epistemic and personal virtues of a good scientist and even (perhaps especially) the merits of careful observation and the study of science for the layman.3 Science, Herschel writes, is exceptional in “filling us, as from an inward spring, with a sense of nobleness and power which enables us to rise superior to” the circumstances of our lives.4 The Preliminary Discourse was printed and bound inexpensively, widely sold, and frequently reprinted.5 Given its history, it seems likely that philosophers of science have been too quick in reading this work primarily through the lens of its contributions to the epistemology of science.

John Herschel was a political radical in the utilitarian mould but no social leveller. Indeed, he was highly ambivalent over the notion of ‘democracy’ and feared it could unleash the tyranny of the masses. Rather, like his one-time close friend Charles Babbage, he was a rational materialist reformer with little sympathy for old state props such as the Church of England and the prevailing curriculum of the elite Anglican universities. This periodically put him at logger heads with contemporary Cambridge and Oxford taught men. (Herschel had graduated from Cambridge as senior wrangler in 1813 and Babbage was awarded a Cambridge degree with no examination in 1814.)

From 1833 to 1838, John Herschel relocated himself, his growing family, and one of his father’s largest telescopes to the British colony of Cape Town, in South Africa, with the intent of undertaking the most thorough observational study of the southern heavens ever made. This endeavor was driven in part by his desire to complete the astronomical work begun by his father William, whose own astronomical surveys had been confined to the northern hemisphere. The southern heavens had been previously mapped by Edmond Halley (1656–1742) and the Abbé Nicolas-Louis de Lacaille (1713–62), but their surveys were primarily undertaken for navigational purposes and with comparatively small telescopes.

An aspect of John Herschel’s science not widely appreciated was his complex view of Earth as a planet and as our entry point for understanding physical and chemical processes everywhere in the universe. Herschel was a crucial and consistent voice in bringing both the astronomy and physics of Newton and the most recent chemistry to bear on the Earth. In this chapter, I provide a view of Herschel’s evolving interest in the Earth and in geology. I present his interaction with the Earth sciences as a unifying thread running through his life, pulling together aspects of his work that otherwise may seem disparate activities. I examine Herschel’s formation as a geologist and a scientific traveler. Lastly, I discuss some of the ways that Herschel’s background in physics, chemistry, and astronomy affected his understanding of geology. Herschel sought to understand the cosmos both by looking up at the stars and down at the Earth.

If anyone symbolized what it meant to “be scientific” and “do science” during the Victorian period, it was John Frederick William Herschel. Born on March 7, 1792, into astronomical royalty as the only son of William Herschel (1738–1822) and Mary Baldwin-Pitt (1750–1832), John was heir apparent to a scientific legacy that included the construction of immense telescopes and the discovery of hundreds of new celestial objects – including the solar system’s first new planet, Uranus. Yet John would prove to have an even longer, broader, and more influential career than his famous father. During a lifetime that spanned Britain’s entire age of reform, he achieved fame as a mathematician, chemist, optical experimentalist, astronomer, and public spokesperson of science. From his early contributions importing and developing advanced Continental mathematics into England, to laying the chemical foundations of photographic development with his discovery of hyposulfite “fixer,” to extending and establishing the pioneering work of his father and his aunt, Caroline Herschel (1750–1848), in sidereal astronomy, John Herschel came to embody the pursuit of natural knowledge in the nineteenth century.

By January 1839, when the daguerreotype was first made public, John Herschel had long been familiar with the basic chemical and optical components necessary to begin his own photographic experiments. His use of visual expression in his observations, combined with his experiments on chemistry, light, and optics, had begun two decades or more before Louis Jacques Mandé Daguerre (1787–1851) and William Henry Fox Talbot (1800–77) made their respective claims to photographic invention. Because Herschel’s photography has been studied largely through the lens of the history of photography, discussions are often inflected by various origin stories that privilege, for better or worse, the creation of recognizable, fixed images. This frame truncates the full and lifelong series of experiments that were eventually to become Herschel’s “photography,” which became a collective heading under which he consolidated his chemico-optical experiments, gathering them into a single strand of research that began as early as the 1810s and persisted through the end of the 1850s. In this extensive group of experiments, Herschel made systematic use of photography for spectral analysis and chemical sensitometric testing long before the photo-chemical work of Henry Roscoe (1833–1915) and Robert Bunsen (1811–99) in Manchester and even longer before Ferdinand Hurter (1844–98) and Vero Charles Driffield (1848–1915), who between them established important benchmarks in the nascent field of photochemistry and sensitometry.1 Signaling that he recognized the direction his experiments on light were taking away from trends in photography by the 1850s, Herschel renamed his use of photography for light experiments “actino-chemistry,” differentiating it from making optical images.2

Precise measurement and the production of accurate standards was at the very heart of John Herschel’s conception of science. This was not only true of his own endeavours, including those astronomical, but was fundamental to his philosophical vision of scientific practice, as well as his theological understanding of nature and God’s role in Creation. Throughout his career, Herschel contributed to several standardizing projects, including the production of units of weight, distance, time, musical pitch, volume, and even the harmonic division of musical notes. In the one full-time position of paid employment that he occupied, as Master of the Mint, he was responsible for regulating the nation’s standards of bullion and coinage and, in his role as a trusted scientific advisor to the British government, he promoted standardized practices for global investigations of natural phenomena, including those astronomical, metrological, and magnetical. To establish accepted units of measurement and standardizing regimes brought order to philosophical inquiry, regulation to the nation and empire’s economic activity, and organization to diverse societies around the world. In his promotion of worldwide investigations into natural phenomena through standardized observation techniques and disciplined observatories, Herschel ensured that the cultivation of nineteenth-century natural philosophy was inseparable from the wider proliferation of empire: science was a tool of British imperialism, providing knowledge on a global scale and bringing together colonial territories in the pursuit of new understandings of nature. By the time of his death in 1871, few had done more than Herschel to facilitate accurate measurements of nature; and given that precise measurement was increasingly to define scientific practice throughout the nineteenth century, his standardizing efforts were remarkable in their influence. Crucially, however, Herschel was implicit that knowing nature through accurate measures and with standardized units was, in itself, of intrinsic moral value: to count molecules, weigh matter, and record the order of celestial motions was to know God and understand the universe that He had created.