a1 Department of History and Philosophy of Science, University of Cambridge, Cambridge CB2 3RH.
During high summer 1721, while rioters and bankrupts gathered outside Parliament, Robert Walpole's new ministry forced through a bill to clear up the wreckage left by the stock-market crash, the South Sea Bubble, and the visionary projects swept away when it burst. In early August the President of the Royal Society Isaac Newton, a major investor in South Sea stock, and the Society's projectors, learned of a new commercial scheme promising apparently automatic profits, a project for a perpetual motion. Their informants were a young Viennese courtier Joseph Emmanuel Fischer von Erlach, a contact of Desaguliers recently engaged in industrial espionage in northern England, and the Leiden physics professor Willem 'sGravesande, who had visited London five years earlier. They reported that they had been summoned to a remarkable series of demonstrations in the castle of Weissenstein, the seat of the Landgrave of Hesse-Kassel. In a carefully guarded room of the castle there was set up a hollow wooden wheel covered in oilcloth, about 12 feet in diameter and 18 inches thick on an axle 6 feet in length. Its designer, a Saxon engineer and clockmaker Johann Bessler, who travelled Germany under the name Orffyreus, had been in Kassel for four years, published schemes for perpetual motion and been appointed commercial councillor. The Landgrave, well-known as a patron of advanced engineering schemes, commissioned him to build a new machine and put it on show before expert witnesses (Figure 1).