and member of the British National Committee for Physics of the Royal Society. In 1978, he retired, retaining emeritus status until his death. He died in St Andrews in Fife of a stroke. Allen received an honorary doctorate from Heriot-Watt University in 1984. The building of the School of Physics and Astronomy of the University of St Andrews is named after John Allen, as is the library in the J.F. Allen building. Allen died of a stroke on 22 April 2001. Family Allen married his wife, Elfriede Hiebert, in 1933. The two divorced later. They had one adopted son. Scientific work During his work on low temperature physics, Allen developed a number of techniques that are still in use today. In 1937, he introduced the O-ring for use as a seal for vacuum systems. He further invented in 1947 indium gaskets to create leak tight seals for low temperature applications. In 1937, Allen discovered superfluid helium together with his student Don Misener in the Mond laboratory in Cambridge, independent of Pyotr Kapitsa in Moscow. His student, Ernest Ganz, later observed the second sound in liquid helium, and Allen and his collaborator possibly also measured the third sound that occurs in thin films, however they did not report their results. When World War II broke out and he worked on projects supporting the army. During World War II, this included the development of on-board oxygen generators for bombers, and a variable time fuse for anti-aircraft shells. Allen also used a movie camera to film his experiments, such as the superfluid helium fountain, which he discovered in 1938 with the help of a pocket flashlight. Over a ten-year period Allen made a movie of the various two-fluid phenomena exhibited by liquid helium-4. The photography of these effects was a real challenge, because liquid helium-4 is essentially transparent. This unique colour movie (the fifth edition was completed in 1982) is one of Allen's great legacies to physics. His was an early user of moving images to document experiments and inform students and the general public. Pictorial biography See also Timeline of low-temperature technology John Allen's video on superfluid helium References Canadian physicists Fellows of the Royal Society Fellows of the Royal Society of Edinburgh People from Winnipeg Canadian people of Scottish descent Scottish physicists Academics of the University of St Andrews Canadian expatriate academics in the United Kingdom 1908 births 2001 deaths Superfluidity