Geology Reference
In-Depth Information
he sailed south from Edinburgh, searching the North Sea coastline for outcrops that would
support his ideas. Two colleagues joined him: John Playfair, a professor of mathematics
at the University of Edinburgh, and twenty-seven-year-old Sir James Hall, grandnephew
of the influential president of the Royal Society. Playfair was a former Presbyterian min-
ister steeped in the traditional views of the Scottish church. Hall, a wealthy young man,
supplied a boat and crew for the day, allowing their party to cover far more ground that
they could on foot. Both Playfair and Hall had initially rejected Hutton's idea of an ancient
Earth. Now, after years of discussions, Hutton had begun to convince them that he might
be on to something.
Hutton picked this stretch of coast to explore because he knew the area was composed
of two types of rock—fine-grained gray sandstone and coarser red sandstone. He was con-
vinced that these strikingly different rocks represented two distinct cycles of uplift and sed-
imentation. Somewhere along the coast the two formations would meet, and the eroding
sea cliffs could expose their contact.
They sailed south from Hall's estate along the rocky coast, where high cliffs provided
excellent exposures of the older gray rock. Several headlands down, they passed a sandy
beach where the beds in a red sandstone cliff lay pitched at a twenty-degree angle. But
where did the red rock meet gray rock? Around the next headland they struck gold. At the
base of the cliff, vertical layers of gray rock jutted upward only to encounter the overly-
ing red sandstone. In between the two rock formations lay gray rubble that looked like the
modern beach deposits exposed along the shoreline.
Hutton was ecstatic. The contact between the gray and red rock lay exposed in striking
clarity, and the story it told demolished conventional views. Here was proof of several
rounds of Hutton's grand cycles. Playfair later described the moment in dizzying terms that
evoke a religious epiphany.
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 these wonderful events, we became sensible how much
farther reason may sometimes go than imagination can venture to follow.
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