Downloaded from http://sp.lyellcollection.org/ by guest on September 25, 2021 The age of the Earth and the invention of geological time JOE D. BURCHFIELD Department of Histor); Northern Illinois University, DeKalb, IL 60115, USA Abstract: During Charles Lyell's lifetime the concept of geological time was gradually rendered meaningful through the construction of a heuristic geological timescale, the development of quantitative methods to calculate the duration of that scale, and the acceptance of a quantitatively determinable limit to the age of the Earth. This paper describes a few episodes in the process of 'inventing' the concept of geological time, episodes chosen primarily for their relevance to the work of Lyell. Reflecting on the panoramic record of the Earth's personal time by analogy, by imposing an order, a past exposed to view as he travelled across the constructed memory, on the evidence of external North American continent on US interstate high- events. We make our concept of 'duration' more or way 80, John McPhee observed, 'The human mind less objective by reference to some repetitive may not have evolved enough to be able to quantifiable standard such as a day or a year, but comprehend deep time. It may only be able to our ability to comprehend duration remains measure it' (McPhee 1980, p. 127). Travelling from subjective, both shaped and limited by the east to west in a horizontal plane, McPhee passed conditions of individual experience. Since through the assemblies of rock that contained the geological time, like historical time, lies forever record of the Earth's past in no apparent chrono- outside the scope of our direct experience, our logical order. Rocks of different geological ages concept of geological time is an artefact. It had to were exposed seemingly at random. From time to be created or 'invented'. time, in cuts and tunnels, a more orderly but limited chronological sequence of rocks was exposed in a The invention of geological time vertical plane. To produce McPhee's sense of 'deep time', the record of the rocks had to be assembled In this paper, I will argue that the invention of and interpreted. In this paper I suggest that the geological time involved at least five essential 'invention' (or perhaps more accurately, the 'con- steps: the recognition of the evidence of a suc- struction') of geological time was the historical cession of past events in the static record of the process by which the concept that McPhee calls rocks, the acceptance of a terrestrial age signifi- 'deep time' was first recognized and then rendered cantly greater than the historical record of human- conceptually meaningful, if not truly compre- kind (the notion, however vague, of 'deep time'); hensible. For a working definition of 'conceptually the development of a historical sense of the Earth's meaningful', I will adopt Lord Kelvin's variation past through the construction of a heuristic geo- on McPhee's cogent distinction, namely his famous logical timescale; the creation of quantitative dictum that 'when you can measure what you are methods to calculate the duration of that scale; and speaking about and express it in numbers you know the acceptance of a quantitatively determinable something about it; but when you cannot measure limit to the age of the Earth. Also important was the it, when you cannot express it in numbers, your creation of a new concept of 'historical time' knowledge is of a meagre and unsatisfactory kind: embracing what Stephen Toulmin has called 'the it may be the beginning of knowledge, but you have twin ideas of "periods" and "development"' scarcely, in your thoughts, advanced to the stage of (Toulmin 1962-1963, p. 105). In the sense of step science' (Thomson 1891, pp. 80-81 ). one, the process of inventing geological time began Time has always presented unique conceptual in the seventeenth century with the work of difficulties for scientists and philosophers alike (see Nicolaus Steno and Robert Hooke: in the sense of Kitts 1966, 1989). We experience time only in the steps three and four, it is still going on and has been present. Our sense of the duration of time is sub- particularly vigorous during the past two or three jective, an inference based on our transitory decades (see Berggren et al. 1995). By limiting this perceptions of experienced events and our memory paper largely to British geologists in the age of of the past. We create a concept of external, non- Lyell, I can deal with only a few episodes in the BURCHFIELD, J. D. 1998. The age of the Earth and the invention of geological time. In: BLUNDELL,D. J. & 137 Sco'rr, A. C. (eds) Lyell: the Past is the Key to the Present. Geological Society. London, Special Publications, 143, 137-143. Downloaded from http://sp.lyellcollection.org/ by guest on September 25, 2021 138 ~. D. BURCHFIELD early stages of invention, a few of the steps in Earth has existed, as a world maintaining plants and sketching the preliminary design. animals' (Hutton 1785, p. 3). But, after system- By the time of Charles Lyell's birth in 1797, the atically reviewing the natural causes that he first hints of a notion of geological time had been believed had shaped and continued to shape the appearing for several decades. The pioneering Earth's crust, he was faced with the conclusion that local stratigraphies published by Johann Gottlob ...as there is not in human observation proper Lehmann, Christian F~ichsel and Giovanni Arduino means for measuring the waste of land upon the between 1756 and 1761, for example, all pointed to globe, it is hence inferred, that we cannot an Earth formed by a succession of events rather estimate the duration of what we see at present, than a single act of creation (Albritton 1980, pp. nor calculate the period at which it had begun: so 117-119; Berry 1968, pp. 29-34). None of the three that, with respect to human observation, this suggested that the duration of these events would world has neither a beginning nor an end. require a terrestrial age significantly greater than (Hutton 1785, p. 28) that implied by the Mosaic narrative. Nonetheless, the notion of 'deep time' had already been sug- Hutton had perhaps clarified the problem, but the gested a decade earlier by the Cartesian specu- concept of geological time remained formless. lations of Benoi't de Maillet and the Newtonian Much has been written about the 'birth of cosmology of Georges Buffon, and by 1774 it had geology' in the years that coincide closely with been quantified by Buffon's experimental extrapol- Charles Lyell's youth. I will not attempt to rehash ation from Leibniz's hypothesis of a primordial the many ways in which time was invoked in the molten Earth (Haber 1959, pp. 115-136). Despite conflicts over 'Genesis and geology' and the dis- the controversies aroused by de Maillet's countless putes between the neptunists and plutonists. I will ages for the diminution of the seas and Buffon's suggest only the obvious: that no meaningful more modest 75 000 years for the cooling of the conception of geological time had yet been formu- Earth, by the final quarter of the eighteenth century, lated. Nonetheless, the foundations for such a a growing body of field evidence had begun to conception were being laid (see Rudwick 1996). create an intellectual climate where some notion of The palaeontological researches of Georges Cuvier, deep time was, at least in principle, acceptable J. B. Lamarck, William Buckland and others made (Porter 1977, pp. 157-160). No single event, even the strange inhabitants of the remote past vividly the Noachian deluge, could account for the visual and thus sensibly real. They pointed unmis- complexity of the strata, nor could the succession of takably to a temporal succession of living forms. life revealed by the fossils be accommodated in six Fossils also provided William Smith with one of the literal days of creation. By 1785, this new intel- three principles by which he solved the puzzle of lectual climate was sufficiently widespread to the strata and showed how to correlate its widely inspire William Cowper's acerbic lines: scattered parts. The way had been opened for the record of the rocks to be organized into a single ...Some drill and bore chronological column. The solid Earth, and from the strata there By the second decade of the nineteenth century, Extract a register, by which we learn the identification and systematic classification of That he who made it, and reveal'd its date the fossiliferous strata were underway in earnest. In To Moses, was mistaken in its age (Cowper the two decades between J. B. J. d'Omalius 1785, pp. 166-167). d'Halloy's grouping of the Chalk and underlying Although a long span of time before the advent sandstones and marl into a single Terrain Crr of humans seemed necessary to account both for in 1822 and Roderick Murchison's identification of the record of ancient life preserved in the fossils the Permian in 1841, most of the subdivisions now and for the thickness and complexity of strata designated as systems were identified and arranged exposed by the new field studies, there was no chronologically according to the principle of agreement about the magnitude of the time spans superposition. Also by 1840, Adam Sedgwick and involved. Buffon's quantitative chronology was John Phillips had suggested new names reflecting hardly less controversial than de Maillet's eternal- the temporal progression of life revealed by the ism, and, though speculations on the nature of fossil record - Paleozoic, Mesozoic and Cenozoic - geological causes were sometimes hotly debated, for larger chronological groups of systems scant attention was paid to their rates of action.