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Walker, John


(b. Edinburgh, Scotland, United Kingdom, 1731, d. Edinburgh, 31 December 1803), chemistry, botany, mineralogy, geology, anthropology. For the original article on Walker see DSB, vol. 14.

Walker was one of the most influential natural historians in late enlightenment Edinburgh. After a career as a traveler and a parson naturalist, he went on to become professor of natural history at the University of Edinburgh in 1779. In this capacity he served as the secretary of the Royal Society of Edinburgh’s physical section and as curator for the city’s museum of natural history. Though marginalized by nineteenth- and early twentieth-century historians of science, research from the 1960s onward revealed that Walker made original contributions to the biological and physical sciences. In addition to identifying and classifying new botanical and mineralogical specimens, he diligently campaigned for the Linnaean nomenclature to be adopted in Scotland. By the end of his career, he had amassed one of the largest natural history collections in Europe and had taught more than one thousand students, many of whom would go on to have a substantial impact on nineteenth-century biological and physical sciences as practiced in the British Empire and the United States.

Education and Training. Rev. Dr. John Walker received his secondary education at Canongate High School, Edinburgh. There he was taught to read Latin and Greek and in 1746 he matriculated as a divinity student in the University of Edinburgh. While reading for his degree, he also attended the lectures of Robert Steuart (natural philosophy), Andrew Plummer (chemistry), and, most probably, Charles Alston (materia medica). He graduated in 1749 and he spent the next few years preparing for a career in the Church of Scotland. He was ordained as a minister in Glencorse in 1758 and he was then transferred to a church in Moffat in 1762.

Throughout the 1750s and 1760s Walker worked hard to develop close relationships with members of the Philosophical Society of Edinburgh, especially the Judge Advocate Lord Kames and the physician William Cullen. Under Cullen’s guidance, Walker perfected his knowledge of chemistry and began to conduct his own experiments on marls and mineral wells. In particular, Cullen taught Walker how to track chemical reactions gravimetrically, especially those which involved minerals that were important to mining, agriculture, and materia medica. In 1757 Walker published an article on the chemical composition of mineral water in the Philosophical Transactions, and for the next two decades he split his time between his parish duties in Moffat and his scientific and political interests in Edinburgh. In 1764 his politicking paid off and he was appointed to make an official report on the economic and educational resources of the Highlands and Hebrides. His journey was supported by the church (the General Assembly and Scotland’s Society for the Propagation of Christian Knowledge) and the state (the Board of Annexed Estates). This endeavor involved more than 3,000 miles of travel and resulted in him being appointed to make several more journeys over the next fifteen years, including another substantial northern trip in 1771.

Professorial Career. After returning from his 1764 travels, Walker made an unsuccessful bid for the professorship of natural and civil history at the University of St. Andrews. This left him demoralized and he considered emigrating to the North American colonies. Through the encouragement of Cullen and Lord and Lady Kames, he stayed and continued to gather academic and political patrons. During the mid-1770s Robert Ramsay, Edinburgh’s first professor of natural history, became terminally ill, and Walker mounted a full-scale political battle against William Smellie for the post. In the end, Walker was appointed to the chair in 1779. Keeping with the subject’s long ties to materia medica, the post was attached to the medical school. During his tenure he taught around one thousand medical, arts, divinity, and law students, many of whom came from mainland Europe, the British colonies, and the newly established United States. He divided his lectures into two sections. The first detailed the classification systems that he had constructed for mineralogy, botany, and zoology, that is, the three kingdoms of nature. The second covered meteorology, hydrology, and geology. Walker called these the “Hippocratean” lectures because they addressed environmental factors that the classical physician Hippocrates had linked to health. The course covered a staggering amount of information, and copies of the syllabus were sold by local printers. A book-length version of the lecture heads, Institutes of Natural History, appeared in

1792. Students attended class twice per week; at the end of the year some handed their notes over to a stenographer to be copied and then bound into manuscript volumes that served as reference “books” for the rest of their careers. More than twenty sets of these have been preserved, many of which are housed at the University of Edinburgh.

During the late 1790s, Walker’s eyesight began to fail and he asked one of his former students, Robert Jameson, to help him with the lectures. Jameson obliged and eventually was appointed to the post after Walker died in 1803. In addition to lectures, Walker organized field trips, held tutorials in the university’s Natural History Museum, and actively supported his students when they founded the Natural History Society (1782) and a Chemical Society (1785). Indeed, several of his students also went on to found the Highland Society of Scotland and the Agricultural Society (1792). He was a long-standing member of the city’s Philosophical Society, and he was instrumental in transforming it into the Royal Society of Edinburgh in 1783. In 1794 he was made a Fellow of the Royal Society of London.

Botany. Throughout his entire career, Walker remained interested in botany and agriculture. His early thoughts on the subject were influenced by the work of John Ray and Charles Alston, and as early as 1750 he was collecting and cultivating specimens from Canon Mill Bog near Edinburgh. Over the next three decades he assembled an herbarium, planted gardens, and amassed a sizable collection of field notes. In addition to identifying new species, he was especially interested in botanical hydrostatics and he made one of the earliest known attempts to identify the different genera of aquatic algae. To arrange his specimens, he turned to Carolus Linnaeus’s binomial nomenclature. During the 1760s, Walker exchanged letters with Linnaeus and then successfully nominated the Swede to membership in the Philosophical Society. This nomination, combined with Walker’s superior knowledge of Scottish peat moss, grasses, grains, lichens, willows, and various materia medica simples, established him as a notable British botanist.

For the rest of the century Walker’s advice was sought by leading naturalists, including Thomas Pennant, Sir Richard Pultney, Lord Bute, and Sir Joseph Banks. By the time he started lecturing in the university, he had created a unique classification of Scottish plants from which his botanical lectures drew freely. Thus, though he did not publish a systematic botanical text, his ideas were bequeathed orally to his students. In particular, he developed a close relationship with James Edward Smith, future founder of the Linnaean Society of London. They shared an interest in willows (salix) and they took field trips around the Lowlands. Likewise, Walker encouraged Robert Brown’s early research, which eventually led Brown to write a highly influential work on the movement of particles through botanical fluids (Brownian motion). After Walker died, Charles Stewart (another former student) gathered together several of his botanical manuscripts and edited them into two books titled An Economical History of the Hebrides (1808) and Essays on Natural History and Rural Economy (1812). These essays were recommended as important reference books by several Scottish university professors during the first three decades of the nineteenth century.

Although Walker was an avid botanist, he was an even more enthusiastic mineralogist. As a child he had collected minerals in the Pentland Hills and on the Firth of Forth. As a young cleric he busied himself by assaying soil samples. Unlike his botanical system, he forsook Linnaeus’s use of natural characters (based on color and shape) and turned to chemical characters. In following this path, he aligned himself with the work of Cullen, Joseph Black, and other medical school chemists, and with the mineralogical research tradition led by J. G. Wallerius, Axel Cronstedt, and Torbern Bergman in Sweden. From the 1760s to the 1780s, Cullen, Lord Kames, and Lord Bute helped him acquire specimens for his collection and mineralogy books for his library. During this period he also served as a scientific advisor in the mines of Lords Hopetoun and Cathcart.

Chemical Mineralogy. By the time that Walker started lecturing, he had created his own mineralogical system, which consisted of eighteen classes that were based on chemical characters. Over the next twenty years he added, removed, and renamed species, genera, orders, and classes based upon his own experiments, those conducted by colleagues in the medical school, or those related in recent books, articles, or museum catalogs. The research that he pursued during the 1780s can be traced via the classifica-tory headings listed in the syllabi that he had printed for the mineralogy sections of his lectures: Schediasma fossilium (1781), Delineatio fossilium (1782), and Classes fossilium (1787). His work during the 1790s is evinced in the Institutes and his Systema fossilium (c. 1795); the former being the enormous manuscript catalog that he created for the mineralogy collection in the Natural History Museum. The collection contained minerals from all over the world and was one of the largest in Britain. His 1795 system contained nineteen classes and references to hundreds of sources printed in Europe and the Americas. Walker’s expertise on the subject was readily acknowledged in Scotland and abroad. Joseph Black regularly recommended Walker’s course to his own chemistry students, and James Hutton and John Playfair, two of Edinburgh’s geological theorists, also attended his lectures. Other students included Sir James Hall, Thomas Beddoes, Robert Jameson, and Samuel Latham Mitchell. Like his work on botany, the specifics of Walker’s mineralogical system were given to his students orally.

Geolog. Walker’s chemical approach to minerals strongly influenced how he viewed the form and structure of the globe. In his geological lectures, he taught that the surface of Earth consisted of three different types of strata: primary, secondary, and tertiary. The minerals of primary strata were indurated and exhibited strong bonds of chemical affinity similar to those formed by the cement used by Edinburgh’s farmers and masons. Secondary strata contained softer minerals with weaker bonds of affinity. Tertiary strata consisted of organic remains (such as peat moss) and sedimentary formations, either from river silt or mountain debris. As such, they exhibited little to no affinity. Interacting with the strata of the globe were aerial and aqueous fluids, and Walker addressed these substances in his hydrology and meteorology lectures. In particular, like many medically trained naturalists of his time (including Hutton), he held that water both percolated through and flowed over the earth in a fashion analogous to circulation. As much of the chemistry in Edinburgh’s medical school utilized humid analysis, this created a direct link between material transformations that took place on Earth’s surface and those within the human body. Thus, many of the mineralogical terms that Walker introduced into geology were imported from the medically orientated chemistry of Cullen and Black. This connection was by no means unique, and it was practiced by many of the authors listed in Walker’s reading lists, including Wallerius, Cronstedt, and Bergman. Such an overriding commitment to humid analysis also led Walker (as well as Black) to conclude that primary strata had originally formed from some sort of prehistoric aqueous solution that had subsequently hardened. This solution was not equated with the biblical Flood and, as it occurred before written history, it was hard to determine its temporal framework. As a general rule, most Scottish naturalists of Walker’s generation treated any theory that sought to postulate the pre-primary strata composition of the globe as conjecture, as no empirical evidence existed to support it. Walker advanced this cosmological agnosticism in his lectures. In his private papers, however, he entertained the possibility that causal irregularities may have affected Earth’s form and composition before recorded history.

Anthropology. Walker also maintained a strong interest in what later would be called anthropology. For the Lowland Scots at this time, the language and customs of the Highland and Hebrides clans were sometimes just as foreign as those of Native Americans or East Asians. When Walker traveled through these areas in 1764 and 1771, he took detailed notes not only on the flora and fauna, but also on local rituals, culinary traditions, farming practices, and variations in dialect. He submitted reports on these subjects to the General Assembly and the Board of Annexed Estates. In recognition of his medically relevant observations, the University of Glasgow awarded him an MD in February 1765. Because Walker’s reports also addressed religious literacy and history, the University of Edinburgh gave him a DD the next month. The following year he published some of his travel observations as articles in the gentlemanly Scots Magazine. This strengthened his status as an expert in natural history, and soon Lord Kames engaged him as an advisor in a debate that he was having with Edinburgh’s Lord Monboddo over the classification of human beings and “orang-outangs” (chimpanzees).

During the Enlightenment, many naturalists held that the ability to speak categorically separated humans from other animals. Walker accepted this view, but his connections with the medical school also meant that he was respectably familiar with anatomy and physiology. As a result, he rejected Linnaeus’s use of external morphological characters in favor of internal anatomical characteristics. To counter Monboddo, Kames asked Walker to comment on Monboddo’s belief that it was civilized society, not language or morphology, that separated humans from simians—the difference being of degree and not of kind. Walker advised Kames via consultations and correspondence. He provided counterexamples taken from natural history, medicine, and philosophy to undermine the claim that humans and simians should be classified under the same genus. This nomenclatural separation, however, did not extend any further. Although he acknowledged different races, Walker firmly believed that there was only one human species—an assumption that was no doubt linked to the monogenism promoted in the Bible and other texts from antiquity. This commitment is significant, as Walker did in fact accept that variations could occur in other plant and animal species. The name that he gave to this type of change was evolution. As he promoted this term in his natural history lectures, it should perhaps be noted that he taught Robert Waring Darwin, father of Charles Darwin, and Mungo Park, the famed traveler whose works on Africa were read widely in Britain, Europe, and America.

Later Career. After settling himself into his natural history chair, Walker married Jane Wauchope of Niddrie in 1789. Throughout his entire career, he actively participated in the Republic of Letters. His correspondence increased during the 1780s on account of his professorship and his secretaryship of the physical section of the Royal Society of Edinburgh (1784–1803). From the 1780s to about 1800, he corresponded with Britain’s leading politicians and educators and continued to maintain close ties with the church. In 1782 Lord Lauderdale appointed him minister to Colinton, and from 1790 to 1791 he served as moderator of the Church of Scotland.

At the time of Walker’s moderatorship, the church and the state were jointly collaborating to produce the Statistical Account of Scotland (20 vols., 1791–1799). Local ministers were asked to write articles on the natural history, civil history, and economic (statistic) viability of their own parish. The result was one of the largest scientific publications of late-eighteenth-century Britain. To prepare future ministers for such projects, Walker campaigned for measures that would require divinity students to take a natural history course as part of their degree. He also supported the Statistical Account by writing articles on the parishes of Glencorse and Colinton.

As his eyesight started to fade later in his life, Walker began to write down his reflections about various scientific and artistic matters that had guided or stimulated his thoughts about the natural world. These notes, along with the bulk of his manuscripts, are housed in the University of Edinburgh. After his death on 31 December 1803, he was buried in Canongate Graveyard and his library was auctioned. To accompany the sale, Cornelius Elliot published a list of Walker’s books as A Catalogue of the Books in Natural History with a Few Others, Which Belonged to the Late Rev. Dr. Walker in 1804. Notably, many of the books in the catalog are the very same editions as those cited in Walker’s lectures. In accordance with his will, the proceeds of the sale were divided between his widow and the university.


Most of Walker’s manuscripts are housed in the University of Edinburgh’s Special Collections Department. Adversaria, his personal diary from the 1760s, and Systema fossilium (c. 1795), the catalog of the University of Edinburgh’s mineralogy collection, are housed in the Special Collections Department of the University of Glasgow. Throughout his career, Walker composed many manuscript essays that addressed the natural history of the Highlands and the Hebrides. A good number of these were published posthumously as articles in Prize Essays and Transactions of the Highland Society of Scotland and as chapters in An Economical History of the Hebrides and Highlands of Scotland, C. Stewart, ed. (Edinburgh: University Press, 1808) and in Essays on Natural History and Rural Economy, Charles Stewart, ed. (Edinburgh, 1808). Many of Walker’s published works are listed in a table at the end of Lectures on Geology: Including Hydrology, Mineralogy, and Meteorology with an Introduction to Biology by John Walker, Harold W. Scott, ed. (Chicago: University of Chicago Press, 1966). This list, however, is far from complete and excludes several significant publications, cited below.


“Dr. John Walker’s Report to the Assembly 1–65 concerning the State of the Highlands and the Islands.” Scots Magazine 28 (1766): 680–689.

The Rev. Dr. John Walker’s Report on the Hebrides of 1764 and 1771, edited by Margaret M. McKay. Edinburgh: John Donald, 1980.

“Dr. Walker’s Report concerning the State of the Highlands and Islands.” Scots Magazin 34 (1772): 288–293.

Schediasma fossilium. Edinburgh, n.p., 1781.

Delineatio fossilium. Edinburgh, n.p., 1782.

Classes fossilium. Edinburgh, n.p., 1787.

Institutes of Natural History: Containing the Heads of Lectures in Natural History. Edinburgh: Steward, Ruthven & Co., 1792.

“A Memorandum Given ..... to a Young Gentleman Going to India.” Bee 17 (1793): 330–333.

With W. Torrence. “Number XXI. Parish of Glenncross.” In A Statistical Account of Scotland. Drawn up from the Communications of the Ministers of the Different Parishes. Vol. 15, edited by John Sinclair, pp. 435–446. Edinburgh: W. Creech, 1799.

“Number XXVII. Parish of Colington.” In A Statistical Account of Scotland. Drawn up from the Communications of theMinisters of the Different Parishes. Vol. 19, edited by John Sinclair, pp. 579–591. Edinburgh: W. Creech, 1799.

Letter to Colonel Dirom, Quarter Master General of Scotland, on the Discovery of Coal. Edinburgh: 1800.


Eddy, Matthew D. “Geology, Mineralogy and Time in John Walker’s University of Edinburgh Natural History Lectures.” History of Science 39 (2001): 95–119.

———. “Scottish Chemistry, Classification and the Early Mineralogical Career of the ‘Ingenious’ Rev. Dr. John Walker.” British Journal for the History of Science 35 (2002): 382–422

. ———. “Scottish Chemistry, Classification and the Late Mineralogical Career of the ‘Ingenious’ Professor John Walker (1779–1803).” British Journal for the History of Science 37 (2004): 373–399.

———. “The University of Edinburgh Natural History Class Lists.” Archives of Natural History 30 (2003): 97–117.

Shapin, Steven. “Property, Patronage, and the Politics of Science: The Founding of the Royal Society of Edinburgh.” British Journal for the History of Science 7 (1974): 1–41.

Taylor, G. “John Walker, D.D., F.R.S.E. 1731–1803: Notable Scottish Naturalist.” Transactions of the Botanical Society of Edinburgh 38 (1959): 180–203.

Withers, Charles W. J. “‘Both Useful and Ornamental’: John Walker’s Keepership of Edinburgh University’s Natural History Museum, 1779–1803.” Journal of the History of Collections 5 (1993): 65–77.

Matthew D. Eddy

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Walker, John


(b. Edinburgh, Scotland, 1731; d. Edinburgh, 31 December 1803), geology, botany, religion.

Walker was born into a family firmly convincted of the value education. His father was rector of the Canongate Grammar School; and as a youth Walker was trained in Latin and Greek, reading in those languages at an early age. In addition to his ability in the classics, he developed an interest in minerals before he was fifteen. After finishing studied at his father’s school, Walker studied at the University of Edinburgh, where he prepared for the ministry in the (Presbyterian) Church of Scotland.

In the course of his work, Walker became especially interested, through the influence of William Cullen, in chemistry and mineralogy. He soon realized that the classification of minerals had been sadly neglected and therefore traveled throughout the British Isles, sometimes with Cullen, collecting minerals from mines and rock outcrops. Using his own collection as well as that at the University Museum, he had established an “elementa mineralogiae” by the 1750’s: this classification was later modified to include 323 genera. Among the most interesting of the minerals that he collected in the 1760’s was strontianite, from the mines of Leadhills.

Licensed to preach in 1754, Walker was assigned to his first post at Glencorse in September 1758. He soon met Henry Home, Lord Kames, who became his enthusiastic sponsor. Through this relationship Walker was commissioned to make an extensive study of the Hebrides in 1764. This was neither his first nor his last study of the Hebrides or the Highlands; and it was directly responsible for the preparation of a two-volume book printed posthumously in 1808 by his friend Charles Stewart.

From his first ministry in 1758 until his appointment in 1779 to the chair of natural history at the University of Edinburgh, Walker spent all of his spare time in the study of botany and geology; and his knowledge of Latin and Greek permitted him to read the significant literature in those fields. Walker was greatly influenced by the works of Cronstedt and especially by the contributions of Linnaeus. with whom he corresponded in the 1760’s.

Most of Walker’s botanical and geological papers were published or prepared between 1758 and 1779. A new phase in his life commenced with his appointment as regius professor at the University of Edinburgh, where his first class was enrolled at least as early as 1781.

Walker was an organizer of the Royal Society of Edinburgh and was appointed first secretary of the Physical Section in 1783; he also was active in the organization of the Natural History Society of Edinburgh in 1782. He was a long-time member of the Highland Society of Scotland and, as a result of his great interest in agriculture, formed the Agriculture Society of Edinburgh in 1792. These groups gave him an opportunity to participate in scientific discussions and provided an outlet for the publication of some of his articles.

In his initial lecture to his first class, Walker said: “I am to teach a science I never was taught.” He then proceeded to organize a set of lectures on geology “or the Natural History of the Earth.” From then until the end of his life he gave regular lectures on the various aspects of geology and had a great influence in establishing the science as a discipline in higher education. Three of his most famous students were James Hall, John Playfair, and Robert Jameson. In addition, he influenced the early development of geology in America through his student Samuel Latham Mitchill, who became one of the leading men of American science upon his return to the New York area. Walker was a contemporary of James Hutton, and both were members of the Royal Society.

One of Walker’s cheif contributions was the establishment of geology as an organized classroom subject in an institution of higher learning, and he therefore has a legitimate claim to the title of “Father of Geological Education.” Walker’s classroom methods were essentially those used today: he lectured; distributed syllabuses; established a laboratory; and brought in rocks, minerals, and fossils, which were studied with a microscope. The laboratory work included the study of polished surfaces and a large suite of minerals and fossils. In the study of minerals he used a hardness scale similar to that devised by Mohs thirty years later.

In his lectures Walker discussed the origin of carbonates and differentiated between limestone and marble. In addition, he considered the origin of igneous and sedimentary rocks. Among the common rocks, he paid particular attention to the origin of basalt and granite and to the environment of deposition of such sediments as sand.

One of his classic works was his essay on peat, in which he made an exhaustive analysis of the organic content and origin of this substance. In other papers he affirmed that petroleum occurred in rocks as a natural substance. His discussion of rock structures included accurate definitions of strike and dip as well as recognition of hoirizontal strata overlying titled beds, a condition to which he referred as offlap. Walker described the work of both surface and subsurface water and recognized density stratification of lake water. He wrote about till but did not know of its glacial origin.

Walker collected fossils and used them for demonstration purposes in the laboratory. He classified the methods of fossilization and strongly supported the Linnaean system of binomial nomenclature. He believed that fossils could be used to determine rock chronology and maintained that animals and plants were linked in a common evolutionary chain from the “lowest subject up to the human species…all being linked…by the most beautiful and regular gradation.”


Walker’s writings include “An Essay on Peat, Containing an Account of Its Origin, of Its Chymical Principles and General Properties,” in Prize Essays and Transactions of the Highland Society of Scotland, 2 (1803), 1–137; An Economical History of the Hebrides and Highlands of Scotland, 2 vols. (Edinburgh, 1808); Essays on Natural History and Rural Economy (Edinburgh, 1808; repr. London, 1812), published by Charles Stewart; and Harold W. Scott, ed., Lectures on Geology by John Walker (Chicago, 1965), with a complete bibliography, including MSS.

Two short biographies of Walker are W. Jardine, “Memoir of John Walker, D.D.” in The Birds of Great Britain and Ireland, III (London, 1842), 3–50; and George Taylor, “John Walker, D.D., F.R.S.E., 1731-1803, A Notables Scottish Naturalist,” in Transactions of the Botanical Society of Edinburgh, 38 (1959), 180–203. A portrait is in John Kay, A Series of Original Portraits and Caricature Etchings, III (Edinburgh, 1840), 178.

Harold W. Scott

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