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"A journey of a thousand miles begins with a single step," goes the old proverb. And that was true for one of history's greatest scientists.
In 1831, Charles R. Darwin joined a life-changing expedition – before his voyage on board the H.M.S. Beagle. The botanist John Stevens Henslow introduced the then 22-year old Darwin to 46-year old Adam Sedgwick, a self-educated naturalist and professor of geology and botany at Cambridge University.
Although Darwin had been a student at Cambridge, he seems not to have attended Sedgwick´s lectures on geology there, as he regrets in a later autobiographic note that, "Had I done so I should probably have become a geologist earlier than I did."
At the time, Sedgwick was studying the geology of Wales and invited Darwin to join him at a field trip from Shrewsbury, Darwin’s home town. Sedgwick was especially interested in the stratigraphic succession exposed in North Wales. Sedgwick would later use his collected observations to introduce the geologic epoch called Cambrian - which was named after the ancient Roman name for Wales.
Darwin was interested to acquire the basic skills of geological field work, such as identifying rocks and measuring stratigraphic layers. Darwin became, as he notes to a friend, almost "mad about geology."
He purchased a new clinometer with an incorporated compass to measure the dip and direction of strata, as well as a geological hammer for rock collecting. He then visited Llanymynech (located west of Shrewsbury) alone and started to colour a map which noted outcrops of sandstone and coal.
Sedgwick arrived at Shrewsbury on August 2nd, and over the next few days he visited some outcrops located south-west of the city, where he recognized limestone and volcanic rocks. It’s not clear if he met with Darwin beforehand, but it's certain that both geologists left Shrewsbury on August 5th and ventured north. They then spent a week trying to find the sedimentary formation of the Old Red Sandstone, an assemblage of rocks stretching across Britain.
Sedgwick was interested in the geological formations underlying the Old Red Sandstone, as the age of these rocks was still unknown at the time. According to a large-scale geological map published by George Greenough in 1819, such rocks should be found in the area. However, despite their combined efforts and a meeting in Llangollen with another great geologist, Robert Dawson, they weren't able to find the Old Red Sandstone.
In his autobiography, which was compiled many years later, Darwin said that he left Sedgwick at Capel Curig. However, it is possible that he visited with Sedgwick on the island of Anglesey and even made a short trip to Dublin. (On Anglesey, Sedgwick found the Red Sandstone he was after.) During his voyage on the Beagle, Darwin recognized this type of rock on the Cape Verde Islands Serpentine - and he could have only previously seen it on Anglesey.
In any case, it´s definitely known that Darwin studied (by himself) the volcanic rocks found between Capel Curig and Barmouth. He would later show a lot of interest in similar rocks found on islands of volcanic origin in the Atlantic and Pacific Ocean. He also dedicated an entire book to such volcanic phenomena.
When Darwin returned to Shrewsbury August 29th, a letter from Captain Robert FitzRoy was waiting, offering him a position as gentlemen companion on board of the Beagle. And the rest was history.
But Darwin's lesser-known geology field trip in Wales definitely influenced his observations on that later, more famous, expedition. "This tour was of decided use in teaching me a little how to make out the geology of a country," he wrote.
In fact, during the five years long voyage of the Beagle, Darwin compiled 1.383 pages of notes about geology. By comparison, the biological observations that made him famous comprised a mere 368 pages.
These geological observations will profoundly influence Darwin´s most famous scientific achievement. The gradual formation of volcanoes, the slow subsidence of coral reefs, the rising of the Andes by countless earthquakes over time, the fossils excavated in South America - all of these geological observations enabled Darwin to grasp two fundamental principles needed for his theory of evolution: the ancient age of and the slow, but perpetual changes of the Earth itself.
If the Earth was capable of such profound modifications over time, so had any species living on it, to adapt and survive in an ever changing world.
Interested in reading more? Try:
HERBERT, S. (2005): Charles Darwin, Geologist. Cornell University Press: 485
ROBERTS, M. (2001): Just before the Beagle: Charles Darwin’s geological fieldwork in Wales, summer 1831. Endeavour Vol. 25(1): 33-37