MENDELSSOHN, KURT ALFRED GEORG (1906–1980), British physicist. Mendelssohn was born in Berlin and educated at Berlin University. Forced to leave Germany, he came to Oxford to work at Clarendon Laboratory in 1933 and was the first person to liquefy helium in Britain. Subsequently F.E. Simon, N. Kurti, and H. London came to Oxford and contributed with Mendelssohn to the establishment of the Clarendon Laboratory as an important center of low temperature research. With the advent of World War II the low-temperature apparatus had to be dismantled and Mendelssohn turned to various collaborative projects in medical physics. After the war he resumed his work on low temperatures in collaboration with a succession of gifted research students, many of whom built up graduate schools of their own after leaving the Clarendon, thus making their mark in low-temperature centers all over the world. In addition to his laboratory work Mendelssohn was closely involved with other low-temperature scientists at the international level. He was chairman and founding member of the International Cryogenic Engineering Committee and president of Commission A2 of the International Institute of Refrigeration. He was the founder and editor of the journal Cryogenics, an international journal of low-temperature engineering and research (1961–65). He was elected fellow of the Royal Society in 1951. As "extramural" activities he was especially interested in China and in the sociological and engineering backgrounds of the Egyptian and Mexican pyramids, publishing and lecturing widely on these topics.