The mind seemed to grow giddy by looking so far into the abyss of time.
—JOHN PLAYFAIR
IN THE BEGINNING…
For almost 2,000 years, nearly all scholars followed a literal interpretation of the Bible as their guide for the origin and history of the earth. Even as late as the mid-1700s, natural historians still thought the earth was only a few thousand years old, perfect and unchanging except for erosion and decay brought about by Adam’s sin. According to Church dogma, the world otherwise would have been perfect and unchanging. The thinking of prominent natural historian John Woodward (1665–1728) was typical of his time when he wrote in 1695: “The terraqueous globe is to this day nearly in the same condition that the Universal Deluge left it; being also like to continue so till the time of its final ruin and dissolution, preserved to the same End for which ’twas first formed.”
Ideas about the age of the earth were dictated by biblical dogma. For example, in 1654 James Ussher (1581–1656), the Anglican archbishop of Armagh, Ireland (which was mostly Catholic at the time, so he had few Anglicans to minister to), used the ages of the patriarchs in the Bible to calculate that Creation happened on October 23, 4004 B.C.E. Another scholar, John Lightfoot, placed the time at 9 A.M. (Neither of them explained how days and nights could be recognized before there was a sun or Earth.) Of course, the Bible doesn’t give consistent accounts of how much time lapsed between Creation and Noah’s flood, let alone the time afterward, so a lot of guesswork was involved. Nevertheless, Ussher’s estimate was the pinnacle of scholarship for its time, incorporating what was known of the history of the Hebrews, Babylonians, Persians, Greeks, and Romans, so we must respect this estimate for the honest attempt that it was—even though we now know it was about a million times too short.
THE ENLIGHTENMENT
For more than a century, the power of the Church over European scholarship meant that this estimate was not challenged. However, during the Enlightenment, the hold of religious dogma over scholars and scientists began to weaken. Some, like the Frenchman Georges-Louis Leclerc, count Buffon (1707–1788) in 1779, suggested the earth was as old as 75,000 years, at least 10 times the estimate based on biblical chronology.
In the second half of the eighteenth century, scholars and natural historians began to question the power of both the Church and the aristocrats. They used rationality, evidence, and critical thinking to challenge the powers that be and the way things were. They focused on examining the sources of human knowledge, the justification for the power of governments and religious leaders, and the unquestioned assumptions of past centuries. In France, the Enlightenment was based in the salons and culminated in the great Encyclopédie edited by Denis Diderot with contributions by hundreds of leading intellectuals such as Voltaire (1694–1778), Jean-Jacques Rousseau (1712–1778), and Montesquieu (1689–1755). The Enlightenment in England was first inspired by Isaac Newton’s (1643–1727) transformation of physics and our understanding of the universe. It was also led by John Locke (1632–1704), whose ideas about government and religion were an inspiration to Enlightenment-oriented Americans such as Thomas Jefferson (1743–1826), Benjamin Franklin (1706–1790), and other Founding Fathers. Among these was Thomas Paine, who wrote polemics not only against English rule in the Americas but against religion and the Bible as well. Immanuel Kant (1724–1804) revolutionized the field of philosophy in the German-speaking world, and Gottfried Leibniz (1646–1716) made many advances in science and mathematics, especially the invention of calculus (a slightly different version of which was created by Isaac Newton).
To the surprise of many people, Edinburgh was a major intellectual center and the hub (along with Glasgow) of the Scottish Enlightenment. Nicknamed the “Athens of the North,” Edinburgh featured many neoclassical buildings and had a reputation for learning, like that of its ancient namesake. In Tobias Smollett’s novel The Expedition of Humphry Clinker (1771), one character referred to Edinburgh as a “hotbed of genius,” and historian James Buchan describes it well in the title of his book Crowded with Genius.
Why was such a small provincial city like Edinburgh one of the intellectual centers of the world, surpassing even great cities like London and Paris? As Arthur Herman pointed out in his book How the Scots Invented the Modern World, a number of factors contributed to this ideal environment for free thought and intellectual ferment. The first was the political stability and economic boom that came after union with England in 1707. Scottish traders had become rich with their trans-Atlantic trade (especially in tobacco), and their wealth endowed many institutions, especially universities. Except for the troubles with the Catholic Jacobites and Bonnie Prince Charlie that ended after the Battle of Culloden in 1745, Edinburgh experienced political stability and peace for most of the 1700s. After 1745, the Scots tried hard to emulate the English and to succeed in English society and culture.
A second important influence was the religious climate of the city and the absence of religious persecution. After a young Scotsman, Thomas Aikenhead, was hanged in 1697 for blasphemy, the power of religious leaders in Edinburgh rapidly began to wane. Part of the reason was that Scotland was split between Catholics (especially Scottish royalty and the Highlanders) and the mostly Presbyterian followers of John Knox, who were influenced by the Calvinists, with a minority of Anglicans following England’s official church (the Lowland Scots). This is in contrast to England, where anyone who was not a member of the Anglican Church had little chance of advancement, or France, where the Catholic Church was powerful and the aristocracy was corrupt.
The Presbyterians were great believers in every man reading the Bible for himself, and they instituted public schools throughout Scotland, so that by the late 1700s Scotland had the highest literacy rate in the world. By that time, Scotland had five major universities, while England had only two. There were many newspaper and book publishers. In Scottish intellectual life, culture was oriented toward books. In 1763 Edinburgh had six printing houses and three paper mills, but by 1783 there were 16 printing houses and 12 paper mills. Thus, Edinburgh became a major center for the English-language book trade.
Intellectual life revolved around a series of social clubs that began to spring up in Edinburgh in the 1710s. One of the first and most important was the Political Economy Club, aimed at creating links between academics and merchants. Other clubs in Edinburgh included the Select Society, founded by artist Allan Ramsay (1713–1784), philosopher David Hume (1711–1776), and economist Adam Smith (1723–1790). A later organization was the Poker Club, formed in 1762 and named by the historian and philosopher Adam Ferguson (1723–1816) for its aim to “poke up” opinion on many public issues.
Historian Jonathan Israel points out that by 1750 almost all the major cities in Scotland had an intellectual infrastructure of mutually supporting institutions, such as universities, reading societies, libraries, periodicals, museums, and Masonic lodges. The Scottish network was “predominantly liberal Calvinist, Newtonian, and ‘design’ oriented in character which played a major role in the further development of the transatlantic Enlightenment.” Bruce Lenman says their “central achievement was a new capacity to recognize and interpret social patterns.”
Some of the greatest advances came in philosophy, where the freedom to think and question and argue without religious restraint led to great breakthroughs. Most of the great late eighteenth-century Scottish Enlightenment figures were influenced by the legendary Francis Hutcheson (1694–1746), who was professor of moral philosophy at the University of Glasgow from 1729 to 1746. His ideas inspired many later philosophers, such as Adam Smith, David Hume, Immanuel Kant, and Jeremy Bentham, all of whom emphasized the practical, utilitarian, and realist threads of philosophy, versus the more abstract ideas of the philosophers who preceded them.
JAMES HUTTON
Among the geniuses of the Scottish Enlightenment was the legendary skeptical philosopher David Hume; the economist Adam Smith, whose work The Wealth of Nations first described capitalism; the chemist Joseph Black (1728–1799); James Watt (1736–1819), the co-inventor of the modern steam engine that powered the Industrial Revolution; and a quiet young gentleman named James Hutton (figure 4.1). Hutton was born in Edinburgh on June 3, 1726, and was the son of a prominent merchant and city officeholder. Though Hutton’s father died when his son was quite young, James managed to get an education in the local grammar school and at the University of Edinburgh. Even though he was primarily interested in chemistry, he entered the legal profession. But as a lawyer’s apprentice, he spent a lot of time entertaining his fellow clerks with chemical experiments rather than copying legal documents. He, along with his friend James Davie, was also deeply interested in investigating the manufacture of sal ammoniac (now known as ammonium chloride, NH4Cl) from coal soot. As a result, Hutton was released from his law apprenticeship before his first year was out, and he turned to the study of medicine, as it was the only way at that time to study chemistry or any other kind of natural science. He spent 3 years at the University of Edinburgh, then two in Paris, and finally was granted a medical degree in Holland in September 1749. (His departure to Paris also allowed him to escape scandal back home in Scotland for fathering an illegitimate child.)
Figure 4.1
Portrait of James Hutton. (Courtesy of Wikimedia Commons)
But the actual practice of medicine held no appeal for Hutton. His association with Davie in developing an inexpensive method for the manufacture of sal ammoniac proved successful and profitable, and this business then allowed Hutton to take time to manage his family’s farms, especially the one known as Slighhouses in Berwickshire, Scotland. He used his training to experiment with the latest techniques in agriculture with great success. Clearing the landscape, cutting ditches, and draining his farm created many fresh cuts into the local bedrock, which fascinated him. In 1753 he wrote that he had “become very fond of studying the surface of the earth, and was looking with anxious curiosity into every pit or ditch or bed of a river that fell in his way.” By 1765 the farms and the company producing sal ammoniac were prospering, and he had enough income to leave the work to tenant farmers in 1768. He then moved back to Edinburgh to follow his scientific interests.
Hutton had inherited his father’s properties and had income from the farms and the sal ammoniac business, so he had no need to work for a living. As a result, he had plenty of free time to socialize with his friends, particularly Adam Smith and Joseph Black. Together, they formed another discussion group, the Oyster Club, which met every Friday afternoon at two but at a different tavern each week, since the meetings were often a bit too popular. There they would convene to discuss art, architecture, philosophy, politics, physical science, and economics, each giving a brief update on his special project. The discussions were, in Hutton’s words “informal and amusing despite their great learning.” Other members included James Watt and John Playfair, a mathematician who became Hutton’s main disciple among geologists, and many other scholars and natural philosophers from the university. When he visited Edinburgh, Benjamin Franklin was treated as an honored guest. A Swiss chemist who visited Edinburgh described the Oyster Club in these words: “We have a club here which consists of nothing but philosophers. Drs. Adam Smith, Hutton, Cullen, Black, Mr. McGowan belong to it, and I am also a member of it. Thus I spend once a week in the most enlightened and agreeable, cheerful and social company.”
UNIFORMITARIANISM
As a gentleman-farmer and landowner maintaining and improving his family’s farms in southeast Scotland, Hutton had studied how soils form, how sediments erode, and how layers of sediment are deposited as they flow down rivers and into the sea. From this, Hutton gained insights about rock weathering, and how slowly sediments are formed and deposited. He visited the ancient Roman fortification near the Scottish–English border known as Hadrian’s Wall (figure 4.2) and noticed that it had not weathered or broken down much in the more than 1,600 years since it was built in 122 C.E. From this, Hutton realized that the process of weathering down whole mountain ranges would take much longer.
Figure 4.2
When Hutton visited it in the 1770s, Hadrian’s Wall had not eroded or changed significantly in the more than 1,600 years since it was built by the Romans in 122 C.E. This convinced Hutton that the processes that wore down entire mountains must be incredibly slow. (Photo by the author)
Hutton devoted his time to extensive scientific reading and traveled widely to inspect rocks and observe the actions of natural processes. Using the basic principle of natural law that all Enlightenment scholars followed, Hutton applied the principle of naturalism to the earth as well. In his mind, supernatural catastrophes (“catastrophism”) such as the biblical deluge of Noah were useless as scientific explanations, because they could not be subjected to test and examination by natural principles or evidence. Instead, Hutton argued that natural laws and processes that operate today must have operated the same way in the past. This is often called the principle of uniformitarianism, or in geologist Archibald Geikie’s words, “the present is the key to the past.” Hutton’s ideas, including the uniformitarian principle, were first formally presented to the Royal Society of Edinburgh in 1785. Two of his papers were published in 1788 in the Transactions of the Royal Society of Edinburgh under the title “Theory of the Earth; or an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land Upon the Globe.” Finally, in 1795 he published a book-length version of Theory of the Earth.
Hutton’s ideas were astonishing and remarkably advanced for their time. By the late 1700s, scholars knew a lot about rocks, strata, and fossils, but there was no general theory of geology. One of the impediments was the still widely held belief that the earth had been created only about 6,000 years earlier, according to the Ussher-Lightfoot interpretation of the book of Genesis. Some geologists thought that sedimentary rocks were formed when immense quantities of minerals precipitated out of the waters from Noah’s flood. Many scholars realized that the destructive processes of erosion were important, but there was no equivalent explanation for the uplift and creation of the landscape.
Hutton gained his greatest insights on how long this process must have taken when he found outcrops of what is now known as an angular unconformity (figure 4.3). To Hutton, an angular unconformity was proof of the immense age of the earth. He saw the tilted layers at the bottom as having once been deposited horizontally on the bed of a stream or the floor of the ocean, then hardened into sandstones and shales, and then tilted vertically by immensely strong forces. The sharp erosional surface cutting through the lower tilted beds must represent their uplift into mountain ranges, and subsequent erosion wearing them down again over millions of years. Finally, the horizontal beds on top represent the accumulation of yet another long piling up of sediments on the bottom of a river or the ocean, which takes millions of years if you assume modern rates of sedimentation. All together, any singular angular unconformity must represent millions of years of time at the minimum, not the 6,000 years that the Bible supposedly indicated.
Figure 4.3
Angular unconformities in Scotland: (A) At Inchbonny in the valley of the Jed Water, south of Jedburgh, showing the way it was drawn by John Clerk for Hutton’s book. The steeply tilted Silurian “schistus” lies beneath an erosional surface that cut across the sandstones and shales after they were tilted. They were then covered by the nearly horizontal beds of the Devonian Old Red Sandstone. (B) The famous angular unconformity at Siccar Point. The beds show the same Silurian “schistus” overlain by Devonian Old Red Sandstone as in Jedburgh. (Courtesy of Wikimedia Commons)
In 1787, Hutton discovered an angular unconformity in the east bank of the Jed Water, just south of the town of Jedburgh (figure 4.3A). As he wrote in 1795,
I was surprised with the appearance of vertical strata in the bed of the river, where I was certain that the banks were composed of horizontal strata. I was soon satisfied with regard to this phenomenon, and rejoiced at my good fortune in stumbling upon an object so interesting to the natural history of the earth, and which I had been long looking for in vain…. above those vertical strata, are placed the horizontal beds, which extend along the whole country.
Hutton continued to explore outcrops around Scotland (see chapter 5) for evidence to support his views later published in Theory of the Earth. He found additional examples of angular unconformities at Teviotdale and on the Isle of Arran, but the exposures were poor and not easy to date. But on his last field excursion in 1788, he took a small boat along the Berwickshire coast with his friends and followers James Hall and John Playfair. He knew that coming down the coast southeast from Edinburgh, the outcrops were the vertically tilted sandstones and shales then called the “schistus” (now known to be Silurian in age, 435 million years old), also exposed below the unconformity in Jedburgh. But if you came up from the south, the outcrops were mainly horizontal beds of the Old Red Sandstone (now known to be Late Devonian, about 370 million years in age). Like any good detective (or geologist), Hutton knew there must be some place along the coast where the two must meet. Finally, he found it at Siccar Point (figure 4.3B).
As Playfair wrote about that momentous day:
On us who saw these phenomenon [sic] for the first time the impression will not easily be forgotten…We felt necessarily carried back to a time when the schistus on which we stood was yet at the bottom of the sea, and when the sandstone before us was only beginning to be deposited, in the shape of sand or mud, from the waters of the supercontinent ocean…The mind seemed to grow giddy by looking so far back into the abyss of time; and whilst we listened with earnestness and admiration to the philosopher who was now unfolding to us the order and series of these wonderful events, we became sensible how much further reason may sometimes go than imagination may venture to follow.
Hutton’s ideas were a huge departure from contemporary geological thinking. He asserted that sedimentary rocks were once sands and muds that had been washed off the land from rivers and into the oceans, accumulated in beds there, and then solidified into rocks. But he argued that the hardening into rocks was due not to the simple precipitation of sand and mud out of a watery solution but rather was due to the effects of pressure and heat, which is what modern geology has confirmed.
Hutton claimed that the totality of these geologic processes could fully explain the current landforms all over the world, and no biblical explanations were necessary in this regard. Finally, he argued that the processes of erosion, deposition, sedimentation, and uplift of mountain ranges were cyclical and must have been repeated many times in Earth’s history. Given the enormous spans of time taken by such cycles, Hutton asserted that the age of the earth must be inconceivably great. As Hutton himself wrote, geologic time is immense and virtually endless, with “no vestige of a beginning, no prospect of an end.” As Stephen Jay Gould wrote, Hutton “burst the boundaries of time, thereby establishing geology’s most distinctive and transforming contribution to human thought—Deep Time.”
FOR FURTHER READING
Broadie, Alexander, ed. The Scottish Enlightenment: An Anthology. London: Canongate Classics, 2008.
Buchan, James. Crowded with Genius: Edinburgh, 1745–1789. New York: Harper Collins, 2009.
Geikie, Archibald. James Hutton: Scottish Geologist. Shamrock Eden Digital Publishing, 2011.
Herman, Arthur. How the Scots Invented the Modern World: The True Story of How Western Europe’s Poorest Nation Created Our World and Everything in It. New York: Broadway Books, 2007.
Hutton, James. Theory of the Earth with Proofs and Illustrations. Amazon Digital Services, 1788.
McIntyre, Donald B., and Alan McKirdy. James Hutton: The Founder of Modern Geology. Edinburgh: National Museum of Scotland Press, 2012.
Repcheck, Jack. The Man Who Found Time: James Hutton and the Discovery of the Earth’s Antiquity. New York: Basic Books, 2008.
Rudwick, Martin J. S. Earth’s Deep History: How It Was Discovered and Why It Matters. Chicago: University of Chicago Press, 2014.
