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MARGINALIA

Vestiges of James Hutton

Keith Thomson

A recent paper announced the discovery of grains of detrital zircon from 4.4 billion-year-old rocks in Western Australia, representing the original continental crust of the earth. This discovery would have been exceptionally interesting to the Scottish geologist James Hutton (1726–97).

It is ironic that Hutton, the man whose prose style is usually dismissed as unreadable, should have coined one of the most memorable, and indeed lyrical, sentences in all science: "(in geology) we find no vestige of a beginning,—no prospect of an end." In those simple words, Hutton framed a concept that no one had previously contemplated, that the rocks making up the earth today have not, after all, been here since Creation.

Although only his contributions to geological theory are remembered, Hutton was a doctor, farmer, mineralogist, chemist and philosopher. He was also a founder of the Royal Society of Edinburgh, to which on March 7 and April 4, 1785, he revealed his thoughts on the history of the earth. Our record of what he said is limited to a 5,000-word Abstract of a Dissertation ... concerning the System of the Earth, its Duration, and Stability. The magical words "no vestige" did not appear in print, however, until a quite different version of his ideas was published in 1788.

The 1785 abstract begins:

The purpose of this Dissertation is to form some estimate with regard to the time this globe of this earth has existed, as a world maintaining plants and animals; to reason with regard to the changes which the earth has undergone; and to see how far an end or termination to this system of things may be perceived, from the consideration of that which has already come to pass.

Here Hutton laid out his thesis that the present land and geological strata are not original but were "formed by the operation of secondary causes"; that the land is constantly being destroyed by the natural processes of erosion; and that a preceding world had similarly been destroyed. He concluded that an "indefinite space of time" had been needed to "produce the land which now appears" from the "consolidation ? by means of fusion" of earlier sediments, and that an equal space of time will be needed to destroy it, while a world to succeed ours is currently being formed at the bottom of the sea. Like their predecessors, these new sediments will eventually be raised up (as a result of the earth's inner heat) and equally inevitably destroyed again. All those processes are identical to those currently in operation on earth and therefore are observable and potentially measurable. However, he stated:

... as there is not in human observation proper means for measuring the waste of land upon the globe, it is hence inferred, that we cannot estimate the duration of what we see at present, nor calculate the period at which it had begun; so that, with respect to human observation, this world has neither a beginning nor an end.

But this was not Hutton's main conclusion in 1785. Projecting the earth as an end-directed system, in orthodox deist fashion, he wrote:

According to the theory, a soil adapted to the growth of plants, is necesarily prepared and carefully preserved; and, in the necessary waste of land which is inhabited, the foundation is laid for future continents, in order to support the system of the living world.

Thus, either in supposing nature wise and good, an argument is found (formed) in confirmation of the theory, or, in supposing the theory to be just, an argument may be established for wisdom and benevolence to be perceived in nature....

Hutton's 1788 THEORY of the EARTH; or an INVESTIGATION of the laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe begins where the 1785 version left off—with the "system." "? the whole presents a machine of a peculiar construction by which it is adapted to a certain end. We perceive a fabric, erected in wisdom, to obtain a purpose worthy of the power that is apparent in the production of it." Such a machine is "constructed upon chemical as well as mechanical principles, by which its different parts are all adapted, in form, in quality, and in quantity, to a certain end; an end attained with certainty or success.? The globe of this earth is evidently made for man." Further, the earth is "not just a machine but also a organised body as it has a regenerative power."

Hutton's new version is still end directed:

... nature has contrived the productions of vegetable bodies and the sustenance of animal life, to depend ... (on) destruction of one continent ... (and) renovation of the earth in the production of another...."

In fact, in Hutton's cyclical "system of the earth," at least three succeeding worlds can be discovered:

... the world which we inhabit is composed of the materials, not of the earth which was the immediate predecessor of the present, but of the earth which, in ascending from the present, we consider the third.... Here are three distinct successive periods of existence, and each of these is, in our measurement of time, a thing of indefinite duration."

And the process continues. He concludes:

... we have the satisfaction to find, that in nature there is wisdom, system, and consistency. For having, in the natural history of this earth, seen a succession of worlds, we may from this conclude that there is a system in nature ... by which they are intended to continue these revolutions. But if the succession of worlds is established in the system of nature, it is in vain to look for anything higher in the origin of the earth. The result, therefore, of our present enquiry is, that we find no vestige of a beginning,—no prospect of an end.

The End of the Line with No End

Hutton's deist subtext places his theory firmly at the end of a long line of "sacred theories" in which (mostly British) geologists attempted to reconcile their findings and theories with the works and wisdom of the Creator. Famously, Thomas Burnet (Telluria theoria sacra, 1681), John Woodward (An Essay toward the Natural History of the Earth, 1695) and William Whiston (A New Theory of the Earth: From its Original to the Consumation of all Things, 1696), among many others, framed sacred theories that reconciled geological discoveries with the the first book of Genesis. Theirs were strictly linear theories proceeding from the Origin, to the first earth, Deluge and the present earth, followed by the final day when the earth will be consumed and men called to judgment. They tried variously to explain the origin of the earth's present stratification, the cause of disruption of the strata, the origins of mountains, the mechanisms (if any) currently changing the structure of the earth, and their possible contribution toward the End of the World. For Burnet, the Flood was the cause of the present broken state of the earth, but that did not explain why the shattered bits were internally structured in the first place. In his progressively decaying world, no new land was produced. Woodward explained the stratification of the earth in terms of an original uniform crust having been dissolved at the Flood and redeposited according to the specific gravity of the constituents. But that did not explain the origin of mountains.

Figure 1. Cathodoluminescence imageClick to Enlarge Image

In 1668, in a paper on earthquakes read before the Royal Society of London, Robert Hooke identified earthquakes as the cause of uplift of the land. In 1669, Steno (Nicolas Stensen) published his De solido intra solidum naturaliter contento dissertationis prodromus (English translation 1671), the first modern analysis of the geological record, where he articulated the concept of superposition of strata. Although it has been claimed that Steno saw a cyclical system in earth history, in fact he outlined a conventional linear narrative, including one major repetition. The earth was first covered with water in which sediments were laid down. These later formed dry land. Next, these rocks were broken up and the Flood repeated the process with new sediments. Thus we can see three kinds of rock—original, first sediments and second sediments. Steno, seeking to "lay down the agreement of Nature with Scripture," lacked (or did not admit) the intellectual breakthrough of predicting that this would be a process that would continue endlessly into the future, or had been repeated more than once in the past.

Figure 2. Ancient zircons were foundClick to Enlarge Image

Hutton's view of "indefinite time" comes from his analysis of earth processes; like Burnet, he found a measure of the slowness of erosion in the rate at which ancient monuments have been worn away. But whence did Hutton derive the idea of "a circularity in the matter of this Globe?" It seems to us obvious to ask: If the earth is constantly being eroded away, is that loss offset by the buildup of sediment (forming new land in deltas for example) or by mountain building? Theories of cycles appear at least twice in early writing about the earth. The elements of a global water cycle were sketched out in the second half of the 17th century by Edmund Halley among others (but not univerally believed, especially by those who thought rivers were recharged underground from the sea). Hutton himself wrote a long treatise on rain in 1795. Like Hutton, Woodward's thesis had been that the purpose of changes in the earth was to maintain a suitable soil for agriculture. On the global scale, he saw the Flood as a mechanism to "retrench and abridge the Luxury and Superabundance of the earth ? and the matter so buried was to be brought upon the Stage once more; being only reserved for the benefit of posterity.?" He went further and made the rain cycle a vehicle for a fantastical recycling of "Terrrestrial Matter" in which soil is in "a kind of Revolution or Circulation," first being washed into the sea and then "returned back again to the earth dispersedly by rain."

All in Balance

The underlying metaphor was, of course, Newtonian. Hooke (whose Lectures and Discourses of Earthquakes and Subterraneous Eruptions were published posthumously in 1705) referred explicitly to the Newtonian balance of forces:

Water is rais'd in Vapour into the Air by one Quality and precipitated down in drops by another.... In the circular Motion of all the Planets, there is a direct Motion which makes them indeavour to recede from the Sun or Center, and a magnetick or attractive Power that keeps them from receeding. Generation creates and death destroys.... All things almost circulate.... We have multitudes of instances of the wasting of the tops of Hills, and of the filling or increasing of the Plains.... It is possible there may have been several vicissitudes of changes wrought upon the same part of the Earth.

Hutton used the same cosmological analogy. His great genius was to see the global scope, and indefinite time scale, of the mechanisms of change operating cyclically on earth. In 1795, he published the unfinished multivolume version of his theory that so many (unreasonably) find unreadable. The first chapter is an expanded version of the 1788 essay, beginning with the same opening paragraph and closing with the immortal "no vestige" sentence. But "no vestige" leaves room for ambiguity. On the one hand, he seems to be saying that the earth is infinitely old and therefore even, as Aristotle thought, eternal. On the other hand, harking back to the language of the abstract, he might merely be saying that we lack the means to discover the age of the earth. As he said eslewhere in the book: "It is in vain to seek for any computation of the time.?" Taken literally, his words state that no vestige of the original rocks that made up the earth can have survived the geological mill (or, as we now know, the plate tectonic smelter). Grains of zircon belonging to that first crust have survived, however, along with Hutton's genius and his most graceful words.

© Keith Thomson


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