This scene, taken directly from an illustration by Louis Figuier in the Wonders of Science, illustrates William Watson’s 1747 experiment on the velocity of electricity in water.

Using a Leyden Jar charged with static electricity, Watson wanted to send an electric shock across the Thames. He invited members of the Royal Society to take part in his experiment: some twenty-five of them joined him, including Folkes, Stanhope and Lord Charles Cavendish. The scientists met at Westminster Bridge; arranged along the Thames, on boats as well as on the banks, they held conducting wires in each hand, which plunged into the Thames, forming an electrical circuit. At the moment of the discharge, they all felt a shock, and noted, with the help of their watches, that the velocity of electricity is almost instantaneous!

Watson described these experiences in his Philosophical Transactions.