* A little update. Extinct has been relatively quiet this summer. The reason is two-fold. First, I (Max) failed to secure an academic appointment for the fall, which means I’ve been dealing with some feelings of professional disappointment and alienation. (Nooo. Also, whatever, it’s fine.) Second— and more important— I’ve decided to use this time to work on a book. The following essay is adapted from a draft of one of the chapters of the manuscript. It’s about something I’ve been interested in for years— the “Great Taconic Controversy.” This is America’s very own stratigraphic controversy to rival the Great Devonian, the Highlands, and the Cambrian-Silurian Controversies (each of which has its own dedicated monograph). Perhaps someday an enterprising historian will write the book on the Taconic question. For now, “Problematica” is written by Max Dresow…

During a recent road-trip to New York, I convinced my wife to swing through the Taconic range: a charming wrinkle of mountains that runs parallel to the Berkshires. It was a terrible idea; we had about sixteen hours of driving in front of us, and this added ninety minutes right at the beginning. (Oh, and I suppose I should mention that we had a three-year-old and a one-year-old in the car with us.) But I wanted to do it, because the Taconics were the focus of perhaps the most acrimonious debate in nineteenth century American geology— a debate that has been largely, and unfortunately, forgotten.*

[* I don’t want to pick on anyone, but I think it’s worth mentioning that a recent— and very good— book on the history of American geology glosses the Taconic controversy in one sentence: “Given the nationalistic nature of naming to which geologists had by now committed themselves, a debate soon erupted about whether there existed in the United States a local version of the Silurian [System]— to be called “Taconic” after a local tribe of native Americans.” But this gets the crux of the debate wrong. Nobody doubted that Silurian-age rocks were well-developed in North America. What was at issue was whether there existed a system of bedded rocks, and even a fossiliferous series, beneath these Silurian rocks.]

Equinox Mountain, part of the Taconic Range, in western Vermont

I’ve wanted to write about the Taconic controversy for years. I’ve even fantasized about writing a monographic treatment— a pale imitation of Martin Rudwick’s Great Devonian Controversy, or Jim Secord’s Controversy in Victorian Geology (about the Cambrian-Silurian debate). That almost certainly ain’t happening; so instead, I’ve written an essay— a hopefully lucid précis of this unwritten text, which condenses the absurd complexity of the debate into something resembling simplicity. This has involved lots of omission. There are simply too many strands of the drama to weave them all into a (small!) tapestry. It has also involved some simplification, although not to the point of distortion. The worst simplifications are unpacked in footnotes; the rest simply stand as necessary sacrifices to the gods of readability.

The essay has three parts. The first is a prologue, which reviews the structure of the (roughly contemporaneous) Cambrian-Silurian debate, and beings to introduce the “Taconic question.” The next is a breezy jaunt through the first forty years of the Taconic controversy, covering the period from about 1840 to 1880. Then, finally, I discuss the resolution of the debate, which owes largely to the efforts of Charles Doolittle Walcott— one of my favorite figures in the history of American paleontology, and, you may recall, the villain of Stephen Jay Gould’s Wonderful Life. It ends abruptly, and without any attempt to wring a philosophical conclusion from the narrative.

If you want a conclusion, let me state one at the outset. Nothing about the Taconic controversy was inevitable. The whole thing needn’t have happened; in fact, it almost certainly wouldn’t have happened were it not for the iconoclastic proposal of one geologist, Ebeneezer Emmons, at first fighting for the Taconic all on his own. It needn’t have continued as long as it did; again, contingent circumstances— involving the intervention of a European paleontologist, Joachim Barrande— rekindled the controversy after it had largely ceased to be a going concern among geologists. And lastly, it needn’t have ended the way it did. In spite of the basic contingency of the debate, we might have had a Taconic System, at least in the United States. The grounds for its recognition were not entirely lacking, especially since many of the conventions of geological nomenclature had not been rigidly codified at the time. Things could have gone differently! Today, the bottom of the Phanerozoic column could have been Taconic–Cambrian–Silurian instead of Cambrian–Ordovician–Silurian. But things went the way they did, so here’s an essay about it.

Prologue: The Cambrian-Silurian debate

During the nineteenth century, the most controversial rocks in the world were the bedded rocks forming the lowest part of the fossiliferous pile (that is, the rocks of the “Lower Paleozoic”). It was all so much fallout from a broken friendship.

Back in the 1830s, two friends, Adam Sedgwick and Roderick Murchison, had set out to tame the stratigraphic jumble known as the Transition series. Sedgwick was Woodwardian Professor of Geology at Cambridge: a mathematically-gifted scholar who the historian Martin Rudwick has described as “a blunt, plain-spoken Yorkshireman… of straightforward principles and genuine piety.” Murchison, by contrast, was a Jane Austen character: a fox-hunting aristocrat and former military officer with ridiculously thin skin and world-conquering ambition. The two had their work cut out for them. At the time, the rocks of the Transition series were the thorniest problem in geology. They were so cooked and folded that little progress had been made in unraveling either their structural complexities or their stratigraphic relationships. Sedgwick and Murchison were determined to change this. So, over several heroic field seasons beginning in 1831, they worked out the general sequence of strata in North Wales (Segwick) and in South Wales and the Welsh Borderland (Murchison). They did this largely independently, so that when they were finished they each had a result, and a series of strata, they could call their own (Secord 1986).

Roderick Impey Murchison (left) and Adam Sedgwick (right)

After several years they were ready to name the rock units they had identified, and so inscribe their names on the foundation of the fossiliferous pile. Murchison went first, calling his formations the “Silurian System” in homage to a warlike tribe that once inhabited southern Wales. Sedgwick followed with his own name, the Cambrian, for a bundle of strata that dipped beneath the Silurian. (Cambria was the Roman name for Wales.) A joint publication in 1835 sealed the deal: “On the Silurian and Cambrian Systems, exhibiting the order in which the older sedimentary strata succeed each other in England and Wales.” It was a major accomplishment, and was celebrated as a milestone in the project of stratigraphic geology. Then, four years later, they did it again, jointly naming the Devonian System that rests on top of the Silurian (Rudwick 1985).

So far, so chummy. But the friends were about to become involved in the bitterest of feuds, leading to their nearly complete personal and professional estrangement. At the heart of the quarrel were fossils, which were much more numerous in Murchison’s Silurian beds than they were in Sedgwick’s Cambrian. As a result, Murchison was better able to correlate his Silurian rocks with rocks outside of Wales, solidifying its claim to “system” status. (The concept of a “system” was at this time in the process of transforming from a local, descriptive category to a means of naming a set of rocks formed during a particular interval of time anywhere in the world.) But the problems for the Cambrian ran deeper than this. In their original publications, neither Sedgwick nor Murchison placed much emphasis on fossils as defining features of their systems. But Murchison eventually came to view his Silurian fossils as a distinctive worldwide fauna, and so to define his system in terms of its characteristic fossils. He additionally took these fossils to be “the first traces of primeval creation”— that is, the very oldest fossils in the fossil record. At which point the progressive annexation of Sedwick’s Cambrian became just a matter of time.

Two plates of trilobites: the first from Murchison’s *Silurian System* (left), the second from Sedgwick and McCoy’s *A synopsis of the classification of the British palaeozoic rocks* (1855)— the work that first characterized a distinctive fauna for the Cambrian System (right)

As it happened, Murchison had included in his Silurian fauna fossils that also occurred in the Upper Cambrian. Sedgwick could adduce no characteristic fossils for the Cambrian System, which he had defined instead on physical evidence. So, to simplify somewhat, Murchison siphoned off those strata from Sedgwick’s Cambrian that were found to contain Silurian fossils, gobbling up more and more of the Cambrian as time went on. Sedgwick compared himself to a man who returned home only to find “that a neighbor [had] turned out his furniture, taken possession, and locked the door upon him.” But there was little he could do. Eventually, Murchison moved to swallow the Cambrian whole, reclassifying all of Sedgwick’s strata as “Lower Silurian” and, in effect, replacing the old term “Transition” with the new term “Silurian.” As he wrote to a friend in 1846, “the Cambrian manor contains after all no animals but what I have got in my preserves, & which have therefore very naturally got my names.” With no characteristic fossils, the Cambrian was being squeezed out of existence.

Egos drove the quarrel. Murchison, the “King of Siluria,” felt that his own prestige was bound up with the glory of his kingdom. Sedgwick felt similarly. John Salter, an associate of both men, tried to adjudicate, the poor thing. But he was from the wrong social class to play peacemaker in a battle of “gentlemen.” Eventually, Sedgwick was able to characterize a distinctively Cambrian fauna from the British Isles, but the debate remained polarized. There could be no backing down, because at its root it was not just a fight about rocks: “it was a controversy about the origin of life, [and] both men ardently desired the honour of showing that geology provided concrete evidence that life indeed had a temporal beginning” (Rudwick 1972).

Murchison’s Silurian “kingdom” in England and Wales

In America, parallel developments were afoot. Just a year after Sedgwick and Murchison’s joint publication, the New York survey got to work ordering the richly fossiliferous deposits of the Empire State. At the bottom of the pile, resting unconformably on the crystalline rocks of the Adirondacks, was the Potsdam sandstone, named after the village of Potsdam, where sandstone beds crop out prolifically along the Raquette River. Higher in the pile were the Trenton limestone, the Utica shale, and the Hudson River group, all bursting with fossils. The New York geologists agreed that these constituted a system, which spanned the part of the column between the primitive basement rocks and the fossiliferous “Secondaries.” But the name “New-York System” arrived too late; the Cambrian, Silurian, and Devonian had precedent. So, when the first state paleontologist, Timothy Conrad, correlated parts of the New York series with Silurian and Devonian strata, his colleagues were happy to apply the British names— even though local names like “Potsdam” continued to enjoy great popularity in America as a means of designating intervals of time (Schneer 1979).

Now, this system of parallel nomenclature was plenty complicated. But the situation grew exponentially more complicated with the commencement of a debate that roiled American geology for forty years. The debate concerned a pile of rocks that ran in a narrow band for approximately 500 miles, north to south. It was centered on the Taconic Mountains of eastern New York, which also gave the debate its name: the Taconic question, or— more dramatically— Great Taconic Controversy. No one was safe. According to one historian, it “affected the lives and careers of every prominent geologist in the United States and Canada” between about 1840 and 1885. Then it was laid to rest by an assistant geologist of the U.S. Geological Survey, Charles Doolittle Walcott.

The Taconic Question

The Taconic controversy began to stir in 1840. That was when Ebeneezer Emmons— one of the major figures in American geology— hatched an explosive idea.

Emmons was a member of the New York Natural History Survey— in many ways, its leading figure. Among his accomplishments, he led the first ascent of New York’s highest mountain, naming it Adirondack, and coined the name “Potsdam sandstone” to designate the lowest member of the sedimentary series (Schneer 1969). At the time, Emmons believed that the Potsdam rested everywhere on “Primary” rock; believed, in other words, that it was deposited, following an interval of non-deposition, on the crystalline basement. He further supposed that no other rocks were deposited between the time the basement rock formed and the time the Potsdam was laid down. So the Potsdam really was the oldest bedded rock in the state. Perhaps it was even the oldest bedded rock in the country, coeval with the oldest rocks of the Cambrian (or Silurian) System. With so much of the country unsurveyed it was impossible to say. Still, in 1840, this seems to have been the position held by a majority of American geologists, including heavy hitters like Emmons and James Hall.

Some major players in the Taconic controversy: Ebeneezer Emmons (top left), James Hall (top right), Henry Darwin Rogers (bottom left), and James Dwight Dana (bottom right)

Then, Emmons demurred. In his official report on the second geological district, he described a belt of rocks “whose width is not more than fifteen miles,” running from Westchester County, New York “through the whole length of Vermont and into Canada as far north as Quebec [City].” Everywhere the rocks were tightly folded, having been caught, long ago, in the vice of mountain building. And they were metamorphosed too, although Emmons downplayed this newfangled concept. Geologists had known about them for a long time, and had come to see them as “disturbed” representatives of the flat-lying strata to the west. But the more Emmons pondered them, the more he doubted that these rocks were indeed contemporaries of the “New-York” strata. The rocks of the New-York system laid flat; those of the belt were inclined. Also, no members of the New-York system were present in the belt, which reposed, Emmons inferred, directly on Primary rocks of the basement. So Emmons made the momentous choice of calling the strata a system— the “Taconic”— and argued that it was the oldest series of bedded rocks in the country, older even than the Potsdam sandstone.

First to object were Henry Rogers and his brother, William. Talented geologists, they had made their bones unraveling the structure of the Appalachian Range: “a compressed, chaotic, ropey enigma… full of overturned strata and… folds so tight that what had once stretched twenty miles might now fit into five” (McPhee 1998). In 1841, Henry read a paper before the American Philosophical Society, in which he argued that the Taconic strata were continuations of the Hudson River group. It’s just that they were so folded and metamorphosed that they no longer resembled the slates and shales of the Hudson Valley. Rogers later refined this position, arguing that the whole Taconic sequence had been overturned, and correlating its constituent rocks with various formations, including the Potsdam sandstone. Still, the drift of the argument was the same. The Taconic strata did not form a discrete system lying beneath the Potsdam. Instead, they belonged smack in the middle of the New-York system: old, but hardly the oldest bedded rocks in the world.

Emmons’s conception of the Taconic System and its bounding unconformities; redrawn from Emmons (1842) for Rogers (1997). Notice the rocks of the New-York system at the left of the figure, from the basal member— the Potsdam sandstone— to the Trenton and Utica slates. In modern terms, these range from middle Cambrian to middle Ordovician in age

From the beginning, two factors made the Taconic question difficult to resolve. First, no one had observed Taconic strata in contact with either the Potsdam sandstone or the Primary rocks of the Adirondacks. Emmons inferred that the Taconic dipped beneath the Potsdam because he observed the second rock in the New-York system, the “Calciferous sandrock,” resting unconformably upon the inclined Taconic slates, and also because the Taconic strata contained no fossils.* But this was hardly a knockdown argument, even if Emmons was right to think that the Taconic rocks formed a discrete package. Its credibility hinged on a pair of assumptions— that the Taconic rocks were indeed a discrete package, and that the absence of fossils reflected the period of deposition, as opposed to the reworking of rocks by heat and strain. Yet these assumptions, while they were difficult for most geologists to accept, were also difficult to refute. Especially since the structure of the Taconic Range was far too complex for Emmons’s contemporaries to master with the tools at their disposal— the second factor. As you approach the Taconics, “[all] obvious regularities of succession and structure are lost” (Schneer 1979). What you find instead is a mash of strata, interfolded and interfelted together, riven by faults and chewed down by erosion. It was too much, even for the Rogers brothers. So everyone was wrong about the structure of the Taconics; and this made accurate historical interpretation basically impossible.

[* If the Calciferous sandrock reposed unconformably on the Taconic slates, this would have meant that a long period of time intervened between the formation of the slates and the formation of the sandrock— long enough for the slates to have become inclined and then planed off by erosion before the sandrock was laid down. (An “unconformity” is a gap in the rock record, here evidenced by the tilting of strata and the abrupt change in rock type.) During this interval of time (the gap represented by the unconformable surface), the Potsdam sandstone would have formed, Emmons thought. So, the Taconic strata must be older than the Potsdam. The inference is complicated, however, by the fact that Emmons did not unambiguously observe “the Calciferous sandrock” of the New-York system, but only a sandstone he identified with the Calciferous sandrock based on lithological similarities.]

“The Taconic System,” by Ebeneezer Emmons, showing the Hudson River shales overlapping the east dipping Taconic slates (the mostly white, highly-inclined strata at the bottom of the section) and the Calciferous Sandstone/Sandrock and Blue Limestone resting unconformably on the slates

The critics rushed out to an early advantage. Along with the Rogers Brothers, there was James Hall, James Dwight Dana, Edward Hitchcock, and William Mather, to name just the most distinguished among them. Even Charles Lyell weighed in, writing in his bestselling Travels in North America, that “The claim of [the] Taconic group to an independent place among the paleozoic formations seems still very questionable.” It was an opposition designed to cow by sheer weight of authority. So, at the first opportunity Emmons expanded his system, pushing its western border nearly all the way to the Hudson River. He surely thought that the extra territory strengthened the Taconic’s claim to system status. But more importantly, it permitted him to begin characterizing a fauna that belonged distinctively to the Taconic— shades of Roderick Murchison. In 1844, Emmons’s associate had discovered two new trilobite species in Greenwich, east of the Hudson. Emmons took them to be older than any fossils found in the New-York system, and said so in a treatise published the same year. His critics, however, were not impressed— especially when James Hall suggested that one of the trilobites was a variant of a form he had described from the Hudson River group.*

[* Here, it seems, Hall was mistaken; but other paleontologists raised difficulties that could only be gotten rid of by basically ad hoc structural interpretations of the Taconic Range.]

*Atops trilineatus*, one of the trilobite species discovered by Asa Fitch in the Hudson Valley (figured in Emmons 1844)

Inevitably, Murchison became involved. Thrilled that New World strata could be correlated with his Silurian formations, he pressured the doyen of American geology, James Dwight Dana, to bury the Taconic. For Murchison, the Taconic question was an extension of his fight with Adam Sedgwick over the Cambrian-Silurian boundary. In both Britain and America, the key question was whether a sedimentary series— and more to the point, a fossiliferous one— existed beneath the Silurian. Emmons played the American Sedgwick, answering that his Taconic fossils carried investigators “back many stages farther in time when life gave vitality to its waters than the Silurian.” The Taconic, indeed, was the first “vital system,” spanning the interval when living things made their debut on the planet.* Emmons was not as concerned with the origin of life as Murchison— his interests were more geological than paleontological. But this hardly mattered. For Murchison, the stakes were the same.*

[* Emmons does not seem to have regarded the Taconic as older than the Cambrian. Most likely he was using the word “system” in the original sense, to designate a package of rocks in some limited area, united by features like shared direction of dip (Yochelson 1993). This meant the Taconic and Cambrian were approximately coeval (or at least the Cambrian and what he termed the “Upper Taconic”). So, the Taconic System in America could coexist with the Cambrian System in Britain; and both were older than the Silurian.]

At this point, Emmons became embroiled in a legal case involving James Hall, which culminated in Emmons’s public humiliation during the libel trial of Louis Agassiz. (Read about it here!) Emmons removed himself to North Carolina, where he continued to make the case for the Taconic as the head of the North Carolina geological survey. With his exile, however, the debate lost much of its sting. Not a few people wondered if the Taconic would fade away, and eventually die along with the increasingly isolated and jaundiced Emmons.

Meanwhile, in Bohemia, the French paleontologist Joachim Barrande had made a remarkable discovery. In rocks originally described as Silurian, he had distinguished a series of three faunas— largely on the strength of trilobites— which he designated “First” (or “Primordial”), “Second,” and “Third.” These quickly gained acceptance as a means of ordering the Paleozoic strata, as did the rough equivalence of the Lower and Upper Silurian with the Second and Third faunas, respectively. It was a hugely important development, not least because it suggested to many that there had to be fossil-bearing strata beneath Murchison’s Silurian. But when trilobites from the Hudson River group landed on James Hall’s desk— trilobites that belonged to the Primordial fauna— Barrande knew he had a problem. The Hudson River group sat smack in the middle of the New-York system. This meant that it ought to have contained fossils from the Third, or “Upper Silurian,” fauna, exclusively. Sensitive to the threat this posed to his three fauna classification, he pressed his American colleagues for information. How confident were they in the dating of these strata? And could it be the case that the rocks were actually pre-Silurian?

Joachim Barrande (left) and Jules Marcou (right)

Letters crisscrossed the Atlantic. In his Paris home, Barrande fretted. He questioned— quite reasonably— whether James Hall was acting in good faith. Then, in 1860, he read a memoir before the Geological Society of France in which he “pronounced the [Hudson River] trilobites unquestionably of Primordial age and characteristic of a great Taconic system extending far below the [Potsdam]” (Merrill 1924). The news hit Yankee geology like a bombshell. At once the Taconic exploded again, with Barrande’s associate, the dyspeptic Jules Marcou, leading the charge. Marcou was a recent transplant to the United States, having settled permanently in the country just seven years earlier. But he seems to have favored the Taconic on patriotic grounds— why should the Brits get to name all the Paleozoic systems? Anyway, his advocacy would keep the Taconic alive for a further twenty-five years, even after Barrande withdrew from the contest in 1861.

In the same year, 1861, a mortar shell burst over Charleston Harbor. Four years later 700,000 people were dead, and the American Civil War had ground to a calamitous end. Emmons, who had instigated a civil war of sorts in American geology, died in 1863. He was buried in Albany Rural Cemetery. If you visit his grave, you will find that he rests next to his great rival, James Hall, who outlived Emmons by nearly thirty-five years.

Still, Emmons lived long enough to see himself partially vindicated. By the end of the war, most parties accepted that he had been right to recognize “Primordial” strata in New York— strata that predated the Potsdam. But few agreed with his second major assumption, that the Taconic strata were a discrete structural package deposited before any member of the New York system formed. The question then became whether enough of Emmons’s Taconic was Primordial to warrant the recognition of these rocks as a system. Needless to say, it was a tough one to answer, not least because the relative ages of many Taconic strata remained difficult to constrain.

Another view of the Taconic Range, from Connecticut

Revelations came fast and thick, throwing light and shade on the question in about equal measure. Structural revelations made trouble for the Taconic; some of its members, at least, were younger than the Primordial period— Lower Silurian, perhaps. But other strata, like the granular quartz rock, were difficult to place (Rogers 1997). At last someone turned up fossils hailing from the original Taconic of 1842. These provoked their own little controversy, but were eventually shown to be Silurian in age. At this point it was clear: the Taconic did not entirely pre-date the New-York system. Yet it retained a base of supporters. Writing in Science, the geologist N. H. Winchell urged “fair-minded geologist[s]” to call any fossiliferous strata “lying below the Potsdam” Taconic. Yes, Emmons had made mistakes— his Taconic strata were not a discrete package of rocks. But his opponents had erred as well, and it was “unfair to Emmons, and to American geology, to insist that [Emmons’s] preliminary mistake should consign to oblivion the great fact that in America, and by an American geologist, was first discovered the primordial zone of geology.” There were fossiliferous strata dipping beneath the Potsdam; Emmons had described them before Barrande characterized his “Primordial” fauna, and before Sedgwick described a distinctive Cambrian fauna; and so these strata should be called “Taconic,” notwithstanding that the name “Cambrian” had been introduced first.

Forty-five years. That was how long it had been since Emmons proposed the Taconic in his report on the second geological district. The system was in difficulty again, as it had been in the 1840s. But onlookers could’ve been forgiven for regarding it as a geological hydra, always sprouting new heads when others were lopped off. That was the state of play when Charles Doolittle Walcott made his decisive intervention in the debate in 1887.

Resolution: Everyone is wrong (or, the Taconic is older, younger and Coeval with the Potsdam)

Charles Doolittle Walcott was a man of no small importance in the history of American science. Richard Fortey has described him as “the ultimate Washington operator, cultivator of politicians and professors alike,” and Stephen Jay Gould notes that “he had his finger— or rather, his fist— in every scientific pot in Washington.” His first major appointment was as the chief paleontologist of the United States Geological Survey, beginning in 1893. Then, just a year later, he was made director, after which followed a parade of honors: election to the National Academy of Sciences, to the American Philosophical Society, and to the American Academy of Arts and Sciences. In 1901 he served as president of the Geological Society of America and participated in the formation of the Carnegie Institution: an important and well-heeled organization for the promotion of scientific research. Then it was on to the Smithsonian, where Walcott became the secretary, or head honcho, in 1907. He “knew every president from Theodore Roosevelt to Calvin Coolidge, some intimately”— in fact, Roosevelt put up a mighty stink when Walcott proposed to leave the Geological Survey for the Smithsonian. He also served as president of the National Academy of Sciences and the American Association for the Advancement of Science; spearheaded the National Advisory Committee for Aeronautics (later rolled into NASA); and did sundry work for the National Research Council, a body founded in 1916 to aid the war effort. Ellis Yochelson said it best: Charles Doolittle Walcott had the most inappropriate middle name in the history of science.

Charles Doolittle Walcott, photographed around the time of his decisive intervention in the Taconic question

Walcott joined the Geological Survey in 1879, following a two year stint as James Hall’s assistant in Albany. For years he steered free of the Taconic controversy altogether. But then, in 1886, the director of the Survey, John Wesley Powell, assigned him to investigate the faunas of the Taconic region, probably at Walcott’s urging.

As the field season began, Walcott traveled first to Albany, then to Williamsburg, Massachusetts, to inspect Emmons’s original Taconic fossils. After that he made his way north along the line of the Taconics, stopping off at Saratoga Springs before hopping a steamer to Ogdensburg, on his way to Potsdam. Crossing into Quebec, he studied William Dawson’s extensive collections at McGill University. Then, it was back to the States, crisscrossing New York and Vermont in pursuit of the Potsdam. There were no silver bullets to be found. Nowhere did Walcott observe any member of the Taconic series in contact with the Potsdam— the same pattern of deprivation Emmons had confronted. But he made a small discovery, which he reported at the 1886 meeting of the American Association for the Advancement of Science. Within the Taconic Range there was a thin body of limestone interbedded with the slates, and within this limestone, “a fauna… that is identical… with the fauna of the Middle Cambrian or Georgia formation.” It was the American primordial again. Privately, he contemplated a compromise solution that would allow the name Taconic to be engraved upon at least some of the rocks that Emmons had claimed for it (Yochelson 1998).

The Taconic question had never been simple, but by this point it had grown extremely convoluted. The exact matter under scrutiny was whether there existed any geological reason to retain the term “Taconic” given the prevailing norms of geological nomenclature. Parts of the Taconic were equivalent in age to the Cambrian; others were coeval with the Silurian. And there was a third British name, too: “Ordovician,” introduced in 1879 to put the Cambrian-Silurian debate to rest. Of course, there were Ordovician rocks in the Taconics— rocks that were older than what remained of the Silurian but younger than what remained of the Cambrian. So one solution was to just use the British names (as even the British survey had yet to do in the case of “Ordovician”), and let the Taconic go gentle into that good night.

Geological map of the Taconic area, made by Charles Walcott (1888)

That was the internationalist solution. The patriotic alternative was to retain the name “Taconic,” but in a limited sense. It could no longer apply to the whole succession that Emmons had delimited— the rocks were too heterogeneous in age to make that an attractive option. But it could still pick out just those strata that contained the Primordial fauna, as well as any strata that could be correlated with these rocks on the basis of structural evidence. So, under the patriotic solution, the Taconic would become the basal member of the Lower Paleozoic, while the (redefined) Cambrian would name all the strata between the Taconic and the Silurian, squeezing the Ordovician out of existence. (Alternatively, the name “Taconic” could be retained for just the middle division of the Cambrian, which was Walcott’s tentative proposal in 1886, and which involved the demotion of the Taconic from the rank of a geological system.)

The patriotic solution made a certain amount of sense. When Sedgwick at last succeeded in characterizing a fauna for the Cambrian, all the forms came from Barrande’s Second fauna. The Third fauna— while not entirely distinct from the Second— belonged uncontroversially to the Silurian. So geologists could have equated the “Taconic” with the First, or Primordial, fauna, as Jules Marcou proposed at the Third International Geological Congress in 1885. But Marcou was thwarted by supporters of the late Murchison, who preferred a Cambrian–Lower Silurian–Upper Silurian sequence to a Taconic–Cambrian–Silurian one. A decision on nomenclature was delayed until the next congress, to be held in 1888. By then, however, Walcott had played his hand.

The crucial year for the Taconic came in 1887. During that year, Walcott combed the Taconic Range, assisted by a corps of fossil collectors on the hunt for new specimens and fossil localities. They were remarkably successful, moving up and down the spine of the mountains, crossing now into Vermont, now into New York; visiting nearly all the sections mentioned by Emmons and many more besides. What emerged was a picture of the region that was even more complicated than Taconic skeptics had entertained, and one that brought the system to its proverbial knees.

A summary of the Taconic series from Merrill’s *First One Hundred Years of America Geology.* Note the big changes between 1842 and 1844, representing the almost complete reversal of the series

Emmons had organized the Taconic into two divisions, which he termed the Lower and Upper Taconic, respectively. The Lower Taconic was a stack of carbonate and quartz rocks: “granular quartz,” limestone, and slate, stacked one on top of the other. The Upper division was a slate sequence, which included the eponymous Taconic slates and the “Black Slate” housing the 1844 trilobites. Prior to the discovery of these fossils, Emmons had regarded the slate sequence as older than the carbonate-quartzite sequence, and the Taconic slates as the basal member of the system. But in 1844 he stood the whole thing on its head, placing the fossil-bearing rocks at the top of the Taconic series, and the carbonate-quartzite sequence at the bottom.

Another figure from Merrill: Emmons’s division of the Taconic into “Upper” and “Lower” series, from 1855

Walcott showed that this was all mixed up (Rogers 1997). To begin at the bottom: the “granulate quartz” was not the oldest member of the Taconic sequence, as Emmons argued after 1844, and did not predate the origin of animal life. Instead, it was fossiliferous, and equivalent in age to large parts of the Upper Taconic, which Walcott regarded as middle Cambrian. The limestone overlying the quartz was also younger than Emmons thought: Trenton age, the same as the trilobites that Walcott had fed to his lathe in the Rust barn. As for the slates comprising the “Upper Taconic,” these ranged in age from middle Cambrian to “Lower Silurian” (today, Ordovician). There were even slates and sandstones coeval with the post-Trenton Hudson River group. So— to simplify— both the Upper and Lower Taconic contained strata that ranged in age from middle Cambrian to Ordovician or Silurian, making them at once older and younger than the Potsdam.* It was a mess, and considerably more complicated than even the critics of the Taconic system had been prepared to argue.

[* A small complication: because of a stratigraphic error, American geologists had the two major zones of Cambrian trilobites backwards: the younger they regarded as the older, and the older the younger. Eventually, Walcott corrected this mistake; and once he did, the “Taconic” strata he regarded as middle Cambrian became lower Cambrian (Yochelson 1998). So both the Upper and Lower divisions of the Taconic actually range from lower Cambrian to Ordovician/Silurian.]

A tabular view of the Taconic System, from Walcott (1888), with proposed correlations. Reproduced in Merrill’s *First One Hundred Years of American Geology*

For Walcott, the mess was decisive. Recall that the question at issue was whether there existed any geological reason to retain the term “Taconic” given the prevailing norms of geological nomenclature. Walcott answered “no.” Writing to Powell in 1887, he concluded that “the Taconic system…. was founded on an error of stratigraphy, [since] a large portion of it belongs to the [Ordovician age] Champlain series, and [the] portions which we now know to be pre-Potsdam were not placed at that horizon on stratigraphic evidence that could be subsequently verified.” He went on to observe that “[the] paleontological evidence upon which we now place the strata of the Upper Taconic as pre-Potsdam was not obtained until long after the publication of the Taconic System in 1842, ‘44, ‘47, and ‘55.” (He was referring to Emmons’s explicit identification of the Black Slate trilobites with members of the Primordial fauna in 1859.) This gave the terms “Cambrian” and “Primordial” priority; of these, “Cambrian” was the better term. So Walcott withdrew his tentative support for the Taconic. In his published remarks, which appeared the next spring in the American Journal of Science, he argued “that geological nomenclature would be benefited by dropping the name entirely” (Walcott 1888).

Walcott was not quite pushing at an open door. Unbelievably, James Hall had thrown his weight behind the “Taconic,” for basically nationalistic reasons— Yankee rocks deserved a Yankee nomenclature, dammit! But after Walcott’s intervention, support for the system collapsed remarkably quickly. Jules Marcou did not bend, nor did the Winchell brothers, Newton and Alexander. But attempts to revive the Taconic at the next International Congress fell on deaf ears (Schneer 1979). No vote on the Taconic was ever held. In the meantime, geologists increasingly used “Ordovician” to refer to rocks containing Barrande’s Second fauna, and “Cambrian” for rocks containing the First fauna.

The Taconic controversy did not end with the fall of a gavel, or with a decisive refutation— a smoking gun smoldering out of a rock section. It just faded away. Marcou continued to rage, but it had no real effect. With most of the original belligerents either dead (Emmons, Rogers, Dana) or disinterested (Hall), there was no reason to throw more fuel on the fire. Then Marcou died, and the embers were finally— many would have said graciously— smothered.

References

Emmons, E. 1842. Geology of New-York, Part II. Albany.

Emmons, E. 1844. The Taconic System, based on observations… New York: Carroll and Cook Printers.

Emmons, E. 1855. American Geology, containing a statement of principles… (Volume 2). Albany: Sprague & Co.

Lyell, C. 1845. Travels in North America. London: John Murray.

McPhee, J. 1998. Annals of the Former World. New York: Farrar, Straus and Giroux.

Merrill, G. P. 1924. The First One Hundred Years of American Geology. New Haven: Yale University Press.

Oldroyd, D. 1990. The Highlands Controversy. Chicago: University of Chicago Press.

Rogers, J. 1997. James Dwight Dana and the Taconic Controversy. American Journal of Science 297:343–358.

Rogers, H. D. 1841. Some observations upon the geological structure of Berkshire, Mass., and the neighboring parts of New York. American Philosophical Society Proceedings 2:3–4.

Rudwick, M. J. S. 1972. The Meaning of Fossils. Chicago: University of Chicago Press.

Rudwick, M. J. S. 1985. The Great Devonian Controversy. Chicago: University of Chicago Press.

Schneer, C. J. 1969. Ebeneezer Emmons. and the Foundations of America Geology. Isis 60:439–450.

Schneer, C. J. 1979. The Great Taconic Controversy. Isis 69:173–191.

Secord, J. 1986. Controversy in Victorian Geology. Princeton: Princeton University Press.

Walcott, C. D. 1888. The Taconic System of Emmons, and the use of the name Taconic in geological nomenclature. American Journal of Science 35:229–242, 307–327, 394–401.

Winchell, N. H. 1886. The Taconic controversy in a nutshell. Science 7:34.

Winterer, C. 2024. How the New World Became Old. Princeton: Princeton University Press.

Yochelson, E. L. 1993. The question of Primordial and Cambrian/Taconic: Barrande and Logan/Marcou. Earth Sciences History 12:111–120.

Yochelson, E. L. 1998. Charles Doolittle Walcott: Paleontologist. Kent State University Press.