Benjamin Franklin’s Clapham Common Experiment

Today anglers sit by Mount Pond on Clapham Common, fishing for the carp that patrol its waters. They’re joined by the occasional heron, and ducks and geese nest on the little island in the pond’s centre. It’s a typical urban park scene, but it is also the place where Benjamin Franklin conducted one of his most famous experiments.

Franklin lived in London between 1757 and 1775 (his house in Craven Street off Strand is now a museum). He was here firstly as a representative of the Assembly of Pennsylvania, attempting to negotiate with the owners of that colony and with the British Government. As the colonies slid towards open rebellion, Franklin desperately (but futilely) tried to wrest concessions from the British.

Although one of the Founding Fathers of the USA, his initial ‘fame’ was as a scientist, his experiments into electricity seeing him elected a Fellow of the Royal Society in London, and he was the man who invented the lightning rod (as well as bifocal glasses). A major figure in the 18th century Enlightenment and the development of science, he continued experimenting throughout his time in London.

Which is why at some point in the late 1760s or early 1770s (we don’t have a precise date), we find him by Mount Pond, a short stroll from Clapham Common Westside, where he was the guest in the house of a friend called Christopher Baldwin*.

The pond seems to have been created in the 1740s, dug out for gravel, the waste stacked on a small hill that became the island in the centre of the lake. In 1748 a banker, Mr Henton Brown, applied to the local parish to enclose the lake for his own use and to build a summerhouse on the island. These privileges were later revoked as other nearby householders tried to carve off slices of the Common for themselves.

(As an aside, the house where Henton Brown lived was later occupied by Henry Cavendish – it becomes known as Cavendish House – another scientist and member of the Royal Society. He and Franklin frequently corresponded.)

The experiment Franklin conducted was to try and replicate something he had seen on a ship as he travelled over to England in 1757, which he wrote about in a letter of 1773

In 1757, being at sea … I observed the wakes of two of the ships to be remarkably smooth, while all the others were ruffled by the wind,… Being puzzled …, I at last pointed it out to our captain, …“The cooks, says he, have, I suppose, been just emptying their greasy water through the scuppers, which has greased the sides of those ships a little;”

Afterwards being again at sea in 1762, … An old sea captain, then a passenger with me, thought little of it, supposing it an effect of the same kind with that of oil put on water to smooth it, which he said was a practice of the Bermudians

In the same letter he writes about the experiment on the Common

At length being at Clapham where there is, on the common, a large pond, which I observed to be one day very rough with the wind, I fetched out a cruet of oil, and dropt a little of it on the water. I saw it spread itself with surprising swiftness upon the surface; … and there the oil, though not more than a tea spoonful, produced an instant calm over a space several yards square, which spread amazingly, and extending itself gradually till it reached the lee side, making all that quarter of the pond, perhaps half an acre, as smooth as a looking-glass.”

“Storm oil” as it is known, works by forming a thin layer across the water’s surface, resulting in a damping effect that stops waves forming so easily. Although known since ancient times and a common practice with seafarers, it wasn’t until 1774 and Franklin’s presentation to the Royal Society of the results of his experiments on Clapham Common and Derwent Water in the Lake District that it became the subject of more detailed scientific investigation. Lifeboats and other vessels carried storm oil almost to the end of the 20th century.

*In a letter to Franklin dated 5 March 1779 Baldwin writes and references the experiment, and also gives one of the first examples of using ‘oil on troubled waters’ in a metaphorical sense. “Think for a moment of the pleasure we have had in smoothing the ruffled surface of the Pond on our Common, between me & neighbour Brown. Oh! that I could join you in pouring oil on a more troubled surface!” 

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