The Reading Room

John Playfair: The Scottish Enlightenment’s Sherlock Holmes of Geological Science

Amid all the revolutions of the globe, the economy of Nature has been uniform . . . and her laws are the only things that have resisted the general movement. The rivers and the rocks, the seas and the continents, have been changed in all their parts; but the laws which direct those changes, and the rules to which they are subject, have remained invariably the same.John Playfair
It surprises me that the great thinkers of the Age of Enlightenment (1685–1815) are not compared more often to Sherlock Holmes. Holmes applied acute observation and reason—deductive logic—to the crime mysteries of London life that visitors brought up the stairs to him at 221b Baker Street. 
Few Enlightenment figures more readily bring this to mind than John Playfair (1748–1819), a virtual archetype of the Scottish Enlightenment. He was the first to conceive and define glaciers and the action of Alpine glaciers over the center of Europe. 
Why an archetype of the Scottish Enlightenment? Playfair was the son of a Scottish clergyman and like so many others (for example, Adam Smith) began as a student of theology. But he became as impassioned about science as Smith did about economics. Works we will discuss earned him a professorship of mathematics at the University of Edinburgh, the beating heart of the Scottish Enlightenment, and then a professorship of natural philosophy (which meant “science”).
One is reminded of Sherlock Holmes because without leaving Scotland, without traveling to the Alps or Switzerland, without seeing them, Playfair deduced the existence and action of glaciers and the impact of the Alpine glaciers. Just as Holmes, attended by Watson, sat in their Baker Street flat and listened to visitors describe their experiences, their observations, and the mysteries that confounded them, John Playfair sat in Edinburgh and read the reports of travelers to the Alps and from the evidence they offered explained mysteries they could not.
Playfair’s involvement began with the death of the celebrated geologist James Hutton, Playfair’s teacher and later his colleague at the University of Edinburgh. Playfair’s first job at the university was to promulgate the ideas of Hutton. He did so by publishing Illustrations of the Huttonian Theory of the Earth, Edinburgh, 1802, a work that brought Playfair fame and is even today considered the basis of modern geology. But even as he espoused Hutton’s theories (just 140 pages of the book), Playfair was thinking his own thoughts to which he devoted 388 pages of notes that rounded out Hutton’s theories.
Like Holmes, he pored over the reported evidence of others. In 1796, six years before publication of the book on Hutton, Horace-Bénédict de Saussure had published his first volume of Voyages dans les Alpes. Here was empirical evidence aplenty. Saussure remarked that the whole country, from the banks of Lake Geneva to the sides of the Jura that face the Alps, was littered with rock fragments and that “the majority of these stones are of granite . . . [and] that the ground on which they have been deposited is of an entirely different kind [schist] . . . and that one cannot help recognizing that these fragments are from a quite different formation torn away from the Alps by some powerful agent which has carried them down to their present position.”
Playfair had his mystery, as did Holmes. Who (or what) did it? In this case, what was the agent? The question came with an answer advanced by the geologist J. A. de Luc. A volcanic explosion had thrown these fragments weighing several tons or more some 20 to 30 kilometers.
No, said Playfair. Deduction points to the conclusion “that water is this agent there can be no doubt.” 
And yet, Saussure was a careful and honest observer, it seems. In his “Journey Round Mont Blanc,” in this same first volume, he describes glaciers as “these masses of ice which slide down the slope towards the valley below, full of pieces of the rocks found at the sides of the glaciers, pieces which form the moraines.” He observes that boulders are dragged to valley bottoms between mountains different from their own. Furthermore, these boulders were “rounded and polished by friction, boulders housed on the glacier, which have retained their keen, sharp ridges.” Honest and painstaking observation by Saussure. But having described the elements of the problem quite clearly, he could not deduce a conclusion. He left that for the master detective, John Playfair, who offered the solution dictated by logic—and did so sitting in Scotland. 
In his notes appended to the Illustrations of the Huttonian Theory of the Earth, he advanced the theory of glacial action:
For the moving of large masses of rock, the most powerful engines without doubt which nature employs are the glaciers, those lakes or rivers of ice which are formed in the highest valleys of the Alps. . . . These great masses are in perpetual motion, undermined by the influx of heat from the earth, and impelled down the declivities on which they rest by their own enormous weight, together with that of the innumerable fragments of rock with which they are loaded. These fragments they gradually transport to their utmost boundaries, where a formidable wall ascertains the magnitude, and attests the force, of the great engine by which it was erected. The immense quantity and size of the rocks thus transported have been remarked with astonishment by every observer. . . . The stones collected on the Glacier de Miage, when Saussure visited it, were in such quantity as to conceal the ice entirely and explain sufficiently how fragments of rock may be put in motion even where there is but little declivity, and where the actual surface of the ground is considerably uneven. In this manner . . .  huge fragments of rock may have been carried to a great distance. ”
That was it. Holmes reached his deduction from the evidence. But as fans of Holmes will know, when required to do so, he got around to see for himself the scene of the crime. Usually in the company of Watson. 
In 1815–16, Napoleon had been defeated, again, and sent into exile, so that peace at last came to Europe. That is when John Playfair undertook a long journey to France, Switzerland, and Italy. With a well-informed guide, Playfair traced the steps of Saussure through the Alpine valleys to see for himself. 
Returning to Scotland, Playfair immediately began to prepare a new edition of Illustrations when he quite suddenly died in July 1819. The intervention of death was an actor in the drama that even the Enlightenment could not defeat.
But Playfair was lucky.  We have the extensive notes on his observations and conclusions in the Alps and upon glaciers today thanks to a kind of biography written by his nephew as a foreword to the Collected Works of the Late Professor Playfair, Edinburgh, 1822. Playfair’s observations in Switzerland and the Alps seemed to confirm entirely the theory he had advanced back in 1802. The foreword by his nephew states: 
“On entering the Val Travers in Mont Jura, he met with a phenomenon . . . which had often engaged his attention, namely the existence of loose blocks of granite . . . on the surface of a chain of mountains entirely calcareous. . . . The largest and most striking of these [he calculated to weigh] 2,520 tons. When we consider that the nearest point where the granite is to be found in its native place is at a distance of 70 miles [112 km] it is clear that this block could not have ‘performed such a journey over intervening hills and valleys. . . . A current of water would have deposited it in the first valley it came to.’ ”
Like most men of the Enlightenment, Playfair began all research with the assumption that the creator of the universe was God and the scientist sought to understand God’s plan. He wrote
The Author of nature has not given laws to the universe, which, like the institutions of men, carry in themselves the elements of their own destruction; he has not permitted in his works any symptom of infancy or of old age, or any sign by which we may estimate either their future or their past duration.
By now, it was 1822, but Playfair’s ideas, just as in 1802, were either ignored or rejected as preposterous.
Leading geologists and physicists—Darwin, von Humboldt, de Buch, Buckland, and Louis Agassiz—were enemies of the glacial theory. They preferred the conclusions of Saussure that floods rushing down from the tops of the Alps had dragged blocks of stone weighing hundreds of tons. These great scientists acknowledged the virtually insurmountable problems with this theory—but could not relinquish the settled views of science.
John Playfair had been dead some twenty-four years when, in 1843, the theory of the extension of glaciers back to prehistoric times had been confirmed incontestably and accepted universally thanks to the 1841 publication of Louis Agassiz’s Études sur les Glaciers.
It was in Switzerland that Playfair’s ideas were promoted by a peasant from the Val de Bagnes (Valais), Jean Perraudin. He urged his observations and conclusions on scientists and engineers. It was the Swiss engineer Ignatius Venetz who urged the theory on a scientist who gave in to the evidence and supported the glacial theory. In turn they converted the great Louis Agassiz when he visited Switzerland in 1836. Playfair’s theory of the glacier and its action, and in particular, the impact of Alpine glaciers on central Europe, became well established. But it all had begun in Scotland, in the ferment of Edinburgh, when John Playfair was first to give a valid explanation of the origin of the wandering boulders and of their transportation far from their original sites.
Hardly “elementary, my dear Watson,” but instead a tour de force by a Scottish Enlightenment “new philosopher” committed to following the facts, the observations, wherever they led. It was a logical demonstration that in time compelled those who followed Playfair.