ON sunnier days during the summers of the 1770s, two men and a dog might be seen climbing the slope in front of Salisbury Crags, which overlook Edinburgh from the east. They would scramble up to a level where the hard bedrock of basalt stood exposed to the open air.
We know about this from the series of sketches left by one of the pair, John Clerk of Eldin. In Penicuik, at his family’s property six miles south of the capital, they made money from coalmines, which triggered his own interest in all that lay underground. But the pursuits of the two were as much intellectual and political as economic.
The Clerk family tree contained an architect of the Treaty of Union in 1707, while a younger generation would bring forth James Clerk Maxwell, the greatest physicist of the Victorian era. Their versatile genes also carried artistic talent, in connoisseurship and in modest abilities of their own. Clerk’s geological drawings, together with more lightsome sketches of him and his companion on their outings, show just where they went and what they discovered.
The companion was James Hutton, a wealthy industrial chemist, known to us better today as the “father of geology”. Born in Edinburgh in 1726, he died there in 1797 and rests in the graveyard of Greyfriars. He went to the high school, then at the age of 14 to the university. His family were merchants, with a bit of land in Berwickshire, too, but they sent him first to learn the law. He spent his entire time on chemical experiments, so was allowed to switch to medicine. He completed his education at Paris and Leiden, like many well-to-do young Scots in those days.
Once he was home again, Hutton set up a factory to manufacture sal ammoniac, or smelling salts, for which he also found a commercial application in the refinement of metals. All of the sal ammoniac then used in Britain was imported from Egypt. Hutton synthesised it by a process he invented, using soot for his raw material.
There was no shortage of that in Auld Reekie, blackened by the smoke of Midlothian’s coal. Hutton would buy it from baffled tronmen, the local chimney sweeps. He made a lot of money. He was hardly middle-aged when he found the independence to do as he really wanted and follow his fascination with geology.
Still, Hutton and Clerk never quite discovered what they were looking for on Salisbury Crags. They did show the hill had a structure not to be guessed from its outward appearance – the surface of hard rock, formed from a volcano, rested on sediment. The information ran counter to conventional geological wisdom, which assumed rock must lie below and sediment above.
That was how the Flood would have left the Earth’s surface for Noah to contemplate.
In fact the crags had long ago been shaped by the intrusion of molten rock between two existing masses, with the upper mass in time eroded away. This was one of many geological processes Hutton was able to define during decades of research. It also became clear to him how impossible it was for all these processes to have been completed within the 6000 years since God was supposed to have created the Earth, or so said the Bible. Whatever the planet’s exact age might be, it had to amount to much more than that. We ought to think not in thousands but in billions or hundreds of billions of years. Even then “we find no vestige of a beginning – no prospect of an end”.
Hutton’s researches finally led him to evidence that made geological history clearer than Salisbury Crags ever could. Down the coast from Edinburgh, Siccar Point was a site in Berwickshire where layers of the oldest rocks on Earth rose in cliffs above the breakers of the North Sea. Nor were they tidy layers, but vertical as well as horizontal, folded and creased and crushed.
Hutton one day took some friends in a small boat to disembark near the headland.
A member of the party, John Playfair, professor of mathematics at Edinburgh, recalled the solemn silence that fell on them as Hutton’s commentary brought home what they were looking at: “We felt ourselves necessarily carried back to the 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 a superincumbent ocean.
"An epocha still more remote, when even the most ancient of these rocks, instead of standing upright in vertical beds, lay in horizontal planes at the bottom of the sea, and was not yet disturbed by the immeasurable force which had burst asunder the solid pavement of the globe.
“Revolution still more remote appeared in the distance of this extraordinary perspective. The mind seemed to grow giddy by looking so far into the abyss of time, and while 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 farther reason may go than imagination can venture to follow.”
In fact, Hutton was the author of an idea far from mysterious, that the history of the world is to be read not from ancient scriptures but from the evidence in present-day rocks. From nearby Scottish landscapes his friends could see how geological features were not static but underwent continuing transformation over infinitely long periods of time. Therefore, contrary to the orthodox religion of his day, the Earth could not be young but must be old.
In God-fearing Scotland this was still quite a startling argument.
The nation had seen in the last couple of centuries some violent religious upheavals, but there were still few Scots who cared to question what the Bible said about the creation of the world and the development of the creatures who lived on it.
Perhaps this could be the wrong way to think about things anyway, since the Bible said besides that all creatures had been created in the beginning on the same pattern as they were to be seen now. Were explorers to take the opposite as true? Or perhaps uniformitarian (to cite the contemporary buzzword) ideas of the time needed no thought because they were false. The buzzword for the opposite was the catastrophic system. People should be careful.
When Hutton went home from his expeditions he continued to live a quiet life in the suburbs of Edinburgh, though he also liked to enliven it in drinking sessions with his fellow intellectuals: David Hume, Adam Smith, Adam Fergusson and the rest of them. We can all regret that they never got fully round to the precise ethical thinking that their theoretical clarity entailed.
