American Scientist

To the Editors:

Lee S. Langston’s Technologue column “The Adaptable Gas Turbine” (July–August) attributed the compression ignition engine to Rudolf Diesel in 1884. To my knowledge, Diesel never held a patent for compression ignition. This distinction goes to Herbert Akroyd Stuart, who held the patents not only for compression ignition, but also for precombustion chambers and direct injection oil engines. Richard Hornsby used a hot bulb addition to Stuart’s design in order to compensate for high-flash-point fuels; later on, Diesel used an injection of compressed hot air in order to achieve the same result. He acquired a patent for this modification, but his use of the Stuart patent was unauthorized. Stuart was never compensated for this use, because Diesel disappeared before it was collected. In 1884, Diesel was busy developing engines that run on gunpowder.

Tony Wilkin
Roxby Downs, Australia

Dr. Langston responds:

Although I do not consider myself an expert on Diesel history, my reference date of 1884 for the Diesel engine—which in its modern form is a compression ignition engine—was taken from C. Lyle Cummins Jr.’s 1976 book Internal Fire. I now see I made a mistake in the date—it should have been 1894! I chose that date because it was the first time Diesel achieved a working model to produce power by using a liquid fuel (page 318 of Cummins). My choice of dates has been based on the initial occurrence of a working model rather than a patent date. In the case of the gas turbine, some authors cite John Barber as the inventor, on the basis of his patent of 1791, but as I pointed out in my column, working models first operated in 1939.