5.3 Hutton's geology: ‘No vestige of a beginning – no prospect of an end’
Geologists are engaged on the business of reconstructing the earth's past and determining the agents of geological change. The only documentary evidence of the earth's origins and ancient past, and of the agents that had caused change, available to Hutton was the book of Genesis, and he had sceptically put it aside, along with miracles. But what if the processes that are presently observable were to be taken as the key to the past? How far might geological enquiry go with the assumption that what is now going on is all that has ever gone on – that the modern world presents an exhaustive catalogue of the processes that have shaped the world, and are continuing to shape it?
Hutton's originality lies in his readiness to go all the way with this assumption. He produced a theory which pictured an earth in which ‘the purpose of a habitable world’ has perpetually been achieved by a set of perfectly balanced agents of natural destruction and renewal. Earth history has no direction: it is now, and always has and will be, in a steady-state. The challenge to the geologist is to show how the steady-state is maintained – to make a survey of the agencies of destruction and renewal at work in the landscape.
What were Hutton's agents of destruction and renewal? Briefly, he argued that rocks are formed at the bottom of the sea and are composed, first, of material eroded from the neighbouring landmasses. Continents are inexorably being eroded away, and their fragments are washed down rivers to the sea. Secondly, rocks are composed of the remains of sea-dwelling animals: calcareous rocks – limestones, chalk, marble – simply are the consolidated remains of countless populations of shellfish whose shells have sunk to the sea-bed. All this material, either from former continents or from former living things, consolidates on the sea-bed where, under pressure from the sea, it is baked by the subterranean heat of the globe (a heat which, in Hutton's view can be reliably inferred from the action of volcanoes). As ancient continents are relentlessly ground away, subterranean heat slowly upheaves sea-beds elsewhere and new continents are born. Nothing is permanent: all is in a flux of destruction and renewal.
In Hutton's account, geological time is directionless – it's not going anywhere: the earth has proceeded from no primeval state, and it will not culminate at some future final point. The steady-state of a habitable world can be projected backwards into the eternal vistas of the past, and can confidently be predicted, stretching into the equally endless vistas of the future. ‘Time’, he wrote, ‘is to nature endless and as nothing’ (Hutton,  1959, vol. 1, p. 15). And in one of the most memorable utterances in the history of geology – one in which Hutton exhibited an uncharacteristic eloquence – he concluded that his researches have shown that the present landscape is built from the materials of former landscapes, which in turn are built from yet earlier landscapes, which in turn stretch back in endless succession. Sounding the standard, eighteenth-century Newtonian note, Hutton wrote:
For having, in the natural history of this earth, seen a succession of worlds, we may conclude that there is a system in nature; in like manner as, from seeing revolutions of the planets, it is concluded, that there is a system by which they are intended to continue those 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 this physical enquiry is, that we find no vestige of a beginning, – no prospect of an end.
(Hutton,  1959, vol. 1, p. 200)
How could Hutton be so confident that he could find ‘no vestige of a beginning’? Other geologists had affirmed that rock strata could be sorted into a single sequence, stretching from ‘primitive’ rocks, formed when the world was young, up to modern rocks. Knowledge of the fossils (remains of living things) which characterise each rock formation was sketchy, but it seemed clear that there were rocks, low down in the sequence, which contained no fossils at all. It seemed reasonable, therefore, to say that the earth has developed uniquely, from a primitive, lifeless condition up to the present. Hutton challenged this by saying that there was, in effect, no such thing as a primitive rock. All rocks, no matter how low in the sequence, no matter how contorted, were formed, he argued, from the sorts of material that are still abundant in the world, and by the processes that are still observably at work in the landscape. If no fossils can be found in them, it is because they have been obliterated by the pressure and the heat which produced the strata.
Hutton's prosaic writing rarely does justice to the huge imaginative leap he made in grasping the explanatory potential of small, mundane modifications to the landscape – like the rolling of rocks downstream by rivers, or the accumulation of seashells on the sea-bed – when these modifications are given indefinite time in which to accumulate. It was remarkable to have been able to contemplate a mountainous country like Scotland, built seemingly of durable and stable rock, as, on one hand, having been built from strata laid down aeons ago beneath now vanished oceans, and, on the other, as potential raw material from which, in the immeasurably distant future, a new continent would be formed.