One of the brightest stars of the Enlightenment was geologist James Hutton, whose wholly original work proved that the world was massively older than the 6,000 years generally assumed at that time. After years of exhaustive work, much of it derided by his contemporaries, he proved the theory that old rocks weather with age and new rocks are formed from their sediment. Some of the rock formations he used to confirm his theory were found at Siccar Point on the coast of East Lothian. Below he describes taking his companions John Playfair and Sir James Hall to show them his evidence. Playfair’s recollections of the day follow his.
Hutton:
Having taken [a] boat at Dunglass burn, we set out to explore the coast. At Siccar Point, we found a beautiful picture of this junction washed bare by the sea. The sandstone strata are partly washed away, and partly remaining upon the ends of the vertical schistus [chrystalline foliated metamorphic rock]: in many places, points of the schistus are seen standing up through among the sandstone, the greatest part of which is worn away. Behind this again we have a natural section of those sandstone strata, containing fragments of the schistus. Most of the fragments of the schistus have their angles sharp; consequently they have not travelled far, or been worn by attrition.
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Playfair:
On us who saw these phenomena for the first time, the impression made will not easily be forgotten. The palpable evidence presented to us, of one of the most extraordinary and important facts in the nature history of the earth, gave a reality and substance to those theoretical speculations, which, however probable, had never till now been directly authenticated by the testimony of the senses. We often said to ourselves, What clearer evidence could we have had of the different formation of these rocks, and of the long interval which separated their formation, had we actually seen them emerging from the bosom of the deep? 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 epoch still more remote presented itself, when even the most ancient of these rocks, instead of standing upright in the vertical beds, lay in horizontal planes at the bottom of the sea, and was not yet disturbed by that immeasurable force which has burst asunder the solid pavement of the globe. Revolutions 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 further reason may sometimes go than imagination may venture to follow.