chalks of Norfolk, fossil claims in the Cheviot hills, he wondered why they were there. He had become preoccupied with the operations of the earth, and he was beginning to discern a gradual and repetitive process measured out in dynamic cycle. (95-96)

Hutton Disproves His Legend

The Traditional argument that Hutton induced his cyclical theory of the world machine from field observations, particularly on granite and unconformities, becomes even harder to understand when we recognize that Hutton's own record clearly belies his legend prima facie.

Simple chronology is evidence enough. Hutton presented his theory of the earth before the Royal Society of Edinburgh on March 7 and April4, 1785, and published an abstract, describing the theory essentially in its final form, later that year. The first full version appeared in 1788, in volume 1 of the Transactions of the Royal Society of Edinburgh, followed in 1795 by the massive (and traditionally unreadable) two-volume Theory of the Earth with Proofs and Illustrations.

Hutton saw his first unconformity in 1787 at Loch Ranza, followed later that year by an example in the Tweed Basin, the subject for John Clerk of Eldin's drawing (Figure 3.1). In 1788, Hutton found his most famous unconformity at Siccar Point, took his friends to see it by boat, and inspired Playfair's awe at "the abyss of time."

When he presented his theory in 1785, Hutton had observed granite at only one uninformative location in the field. That summer, he visited several better sites, including the outcrop at Glen Tilt where he made the key observation (Figure 3.2) of granitic veins intruding the local schists as a thicket of fine fingers. (If granite were a sediment, it could not have forced its way into a thousand nooks and cracks of overlying schist. The granite, Hutton concluded, must have intruded in molten form from below. It must be