The Great Devonian Controversy: The Shaping of Scientific Knowledge among Gentlemanly Specialists
To begin the second act of Gilbert and Sullivan’s Patience, Lady Jane enters a bare set, seats herself before her cello, and in two verses bemoans the changes of increasing age. In the first, or conventional, account, she laments what she has lost with the years, but in the second (speaking mostly of weight) she reports a steady increase: “There will be too much of me in the coming by and by!” The humor of this song plays upon our onesided notion that anything old must become battered, worn, and increasingly bereft of information.
Scholars often make the same false assumption that contemporary cases must provide optimal data, while the records of scientific work steadily decrease in depth and reliability as they grow older and older. We might therefore suppose that, to understand science, a historian or sociologist should study debates and discoveries now in the making. Yet a moment’s thought about our technological age should expose the fallacy in such a position. Our machines have generally made data more ephemeral, or left it simply unrecorded. The telephone is the greatest single enemy of scholarship; for what our intellectual forebears used to inscribe in ink now goes once over a wire into permanent oblivion.
Moreover, in losing the art of writing letters, many scientists have abandoned the written word in a great many previous applications, from diaries (now passed from fashion) to lab notebooks (now punched directly in “machine-readable” format). The present can be a verbal wasteland. Paradoxically, then, our most copious data should, like Lady Jane, occupy a comfortable middle age—old enough to avoid our modern technological debasement, and young enough to forestall the inevitable losses of time’s destruction.
“The great Devonian controversy” occurred during the 1830s, an optimal decade probably unmatched for density of recorded detail. The controversy began with an apparently minor problem in dating the strata in Devonshire; it ended with a new view of the history of the earth. Martin Rudwick can usually trace the course of its enormously varied and complex changes on a daily basis; little more than conversations over ale and coffee, or bedtime thoughts before candle snuffing, seems to be missing. But density of data makes no case for significance on the fallacious premise that “bigger is better.” The subject must also be important and expansive. After a superficial first glance, most readers of good will and broad knowledge might dismiss The Great Devonian Controversy as being too much about too little. They would be making one of the biggest mistakes in their intellectual lives.
I want to state right away how much I respect and admire Martin Rudwick’s book for its rigor, its insights, and its uncompromising intellectual integrity. It is, in a phrase I rarely use, a masterpiece of scholarship. I make this clear because I disagree with its central interpretation of the controversy, and reach a conclusion opposite to Rudwick’s for what. I regard as an interesting (not merely ornery) reason. Only the best books can be praised so highly in the face of basic disagreement.
The geological time scale is a layer cake of odd names, learned by generations of grumbling students by way of mnemonics either too insipid or too salacious for publication: Cambrian, Ordovician, Silurian, Devonian…. Their ubiquity in all geological writing has led students to suspect that these names, like the rocks they represent, have been present from time immemorial (et nunc, et semper, et in saecula saeculorum, amen). In fact, the geological time scale was established in an amazingly fruitful burst of research during the first half of the nineteenth century. In 1800, scientists knew that the earth was ancient, but had no frame for ordering events into an actual history. The primary criterion for unraveling that history—the sequence of unique events forming the complex history of life as recorded by fossils—had not been developed. Indeed, many fine scientists still denied that species could become extinct at all on an earth made properly by a benevolent deity. Geologists of 1800 confronted a situation not unlike the hypothetical, almost unthinkable dilemma that historians would face if they knew that modern cultures had antecedents recorded by artifacts, but did not know whether Cheops preceded Chartres or, indeed, whether any culture, however old and different, might not still survive in some uncharted region.
By 1850, history had been ordered in a consistent, worldwide sequence of recognizable, unrepeated events, defined by the ever-changing history of life, and recorded by a set of names accepted and used in the same way from New York to Moscow. This “establishment of history” was a great event in the annals of human thought, surely equal in importance to the more theoretical, and much lauded “discovery of time” by geologists of generations just preceding. Yet while we celebrate Galileo, Darwin, and Einstein, who beyond a coterie of professionals has ever heard of William Smith, Adam Sedgwick, and Roderick Impey Murchison, the architects of our geological time scale and, therefore, the builders of history? Why has their achievement—surely as important an accomplishment as any ever made in science—been so invisible?
We must resolve this vexatious question in order to appreciate The Great Devonian Controversy, for Rudwick’s seminal book tells the story of how one major period of the earth’s history was recognized and unraveled. That period, the Devonian, occupies the crucial time between 410 and 360 million years ago, when life flourished in the seas, and plants and vertebrate animals became abundant and diverse on land. We will not grasp the importance of this achievement if we follow a common impression and consider stratigraphic geology as “mere description,” to be dismissed as “narrative” in the primitive mode of unquantified storytelling. The Great Devonian Controversy challenges us to understand natural history as a worthy style of science, equal in rigor and importance to the more visible activities of measurement and experiment that set the stereotype of science in the public image. Its success might therefore prompt a broadscale reassessment of science itself as a human activity. The Great Devonian Controversy, in its unassuming and highly technical format, could become one of our century’s key documents in understanding science and its history.
Since the history of science is usually written by scholars who do not practice the art of doing science, they usually impose upon this greatest of human adventures a subtle emphasis on theories and ideas over practice. (I exempt Rudwick, who had a first career as a distinguished paleontologist before switching to the history of science.) The late eighteenth-century Scottish geologist James Hutton, for example, is usually praised as the instigator of modern geology because his rigidly cyclical theory of the earth established a basis for an immense span of time. But Hutton had precious little impact on the practice of geology; his name became an icon, but his theory remained on a periphery of speculation, and the doers of geology largely ignored his contribution and went about their work.
Theory, of course, necessarily permeates everything we do. But it may be pushed below consciousness by groups of scientists who choose to view themselves as ardent recorders of nature’s facts. Early in the nineteenth century, the founders of the Geological Society of London explicitly banned all theoretical discussion from their meetings, and dedicated themselves to what they called the “Baconian” (or purely factual) recording of history. They relegated Hutton and other theorists of past generations to the shelves of speculation, and pledged themselves to fieldwork—specifically to the inductive construction of a stratigraphic standard for history.
When I was younger, and understood science poorly, I bemoaned what I considered the paltry spirit of these men. How could they abandon the exciting ideas, the expansive vision, that motivated Buffon and Hutton, and dedicate themselves instead to finding out what lay on top of what in the rocks? I now appreciate the motives of these men who, after all, forged the geological time scale with their own eyes and hands. Of course they were too extreme (even disingenuous) in their impossible rejection of theory; of course they overreacted to what they interpreted as past excesses of speculation. But they understood the cardinal principle of all science—that the profession, as an art, dedicates itself above all to fruitful doing, not clever thinking; to claims that can be tested by actual research, not to exciting thoughts that inspire no activity.
The younger rocks of Britain and the Continent had yielded with relative ease to consistent stratigraphic ordering—for they are arranged nearly as an ideal layer cake, younger above older, with relatively little distortion by folding, or breakage by faulting, or inversion when older layers thrust over younger strata. But the older rocks, from the Paleozoic Era of our modern time scale (600 million to 225 million years ago), posed greater problems for three major reasons well known to all field geologists: rocks of this age are usually far more contorted by intense folding and faulting; alteration by heat and pressure has obliterated fossils from many units, thus removing the primary criterion of history; large stretches of time lie unrecorded in the rocks, because repeated episodes of mountain building and continental collision destroy evidence.x
The complexity of Paleozoic rocks seriously threatened the stratigraphical research program. If older strata could not be ordered by resolving structure through mapping and by sorting their sequence according to fossils then the science itself was doomed. This ordering, moreover, had great economic importance. The period of great fossil forests or “Coal Measures” (the Carboniferous Period of our modern time scale dating from about 360 to 280 million years ago) lay near the top of this older pile. If geologists couldn’t figure out what came before and after, vast sums of money would be wasted drilling through strata misinterpreted as young but actually older than Coal Measures, in the vain hope of finding coal beneath.
The rocks of Devonshire became a focus for resolving the stratigraphy of older times. Most strata were dark, dense, compacted, and highly contorted—composed of rock known as “greywacke” to quarrymen. Under the lingering tendency to infer age from rock type (an old hope that had failed the test in detail, but had not been abandoned as a rough guide), greywacke smelled old and seemed destined for a position at the bottom of the stratigraphic pile.
The Devonian controversy began in 1834 with a paradoxical claim about fossils supposedly found within the greywacke sequence of Devonshire. Henry De la Beche, later director of the Geological Survey of Great Britain, claimed the discovery of fossil plants within the Devonshire greywackes. (Don’t let the Francophonic name fool you; De la Beche, né Beach, was a proper English gentleman, an important theme in Rudwick’s analysis.) Roderick Impey Murchison, the aristocratic and wealthy exsoldier who had parlayed a taste for outdoor adventure into a serious and fulltime professional commitment, responded in a manner that seemed shockingly inconsistent with the professed empiricism of the Geological Society.