Darwin, rocks and worms

Eden Jackson

Charles Darwin had many interests, many of which became passions. One of these was earthworms and the part they play in the natural world. This passion stayed with him throughout his life and culminated in his snappily-titled final book The Formation of Vegetable Mould Through the Action of Worms.

Rocks, or more accurately geology, were another passion.  Darwin wrote to a friend in 1831 “I am present mad about geology”.  That same year as his studies at Cambridge came to an end he spent time training in field work under Adam Sedgwick, Woodwardian Professor of Geology at Cambridge.  Darwin surveyed and mapped rock at Llanymynech – now a Shropshire Wildlife Trust nature reserve.

Remember that, at this time, geology was a young and developing science.  In the 17th century Archbishop James Ussher deduced from the Bible that creation began on 23 October 4004BC!  Sedgwick classified the Cambrian system of rocks and, despite having a strong Christian faith, held no truck with Ussher’s logic.  However, Sedgwick was never able to accept Darwin’s theory of evolution telling him “I have read your book with more pain than pleasure”.

So, what’s the link between worms and rocks?

There is a story, which I hope is true, that Darwin’s interest in worms was piqued on a visit to Wroxeter.  Just 6miles from his Shrewsbury home, Wroxeter is a huge, hidden Roman city with standing walls and plenty of buried masonry.

True to form, young Charles became curious about how and why this masonry had become partially or wholly buried.  He reasoned that it was through the action of worms over 2 millennia.

When he settled at Down House he ran an experiment to test this theory.  His experiment, known as the worm stone, ran for around 30 years during which time he periodically measured how much of the stone was still above ground until if finally disappeared.  Charles’ son Horace re-ran the experiment to promote his business, the Cambridge Scientific Instrument Company.

Visit Down House today and you’ll see a modern recreation of the worm stone experiment.  Don’t expect to be overwhelmed – it looks like a pile of stones in a field – but if the ghost of Charles Darwin passes by he’ll tell you about the power of worms and the geological history of the stones.