(p. 33) Newcomen and Calley had, in broad strokes, the design for a working engine. They had enjoyed some luck, though it was anything but dumb luck. This didn’t seem to convince the self-named (p. 34) experimental philosopher J. T. Desaguliers, a Huguenot refugee Like Papin, who became one of Isaac Newton’s assistants and (later) a priest in the Church of England. Desaguliers wrote, just before his death in 1744, that the two men had made their engine work, but “not being either philosophers to understand the reason, or mathematicians enough to calculate the powers and to proportion the parts, very luckily by accident found what they sought for.”
The notion of’ Newcomen’s scientific ignorance persists to this day. One of its expressions is the legend that the original engine was made to cycle automatically by the insight of a boy named Humphrey Potter, who built a mazelike network of catches and strings from the plug rod to open the valves and close them. It is almost as if a Dartmouth ironmonger simply had to have an inordinate amount of luck to succeed where so many had failed.
The discovery of the power of injected water was luck; understanding and exploiting it was anything but. Newcomen and CalIey replaced the accidental hole in the cylinder with an injection valve, and, ingeniously, attached it to the piston itself. When the piston reached the bottom of the cylinder, it automatically closed the injection valve and opened another valve, permitting the water to flow out.
Rosen, William. The Most Powerful Idea in the World: A Story of Steam, Industry, and Invention. New York: Random House, 2010.
(Note: italics in original.)