PROF. P. W. BRIDGMAN, research professor of physics at Harvard University, is known to all physicists for his pioneering work on the properties of substances at very high pressures. Bridgman devised new method to withstand high pressures, particularly method of the unsupported area which enables joints to be designed which become tighter than higher the pressure. In the first stage of his work he studied the properties of substances up to pressures of 20,000 atmospheres : the change of volume, the melting and transition points, the viscosity and the electrical properties. As a result of his researches on the behaviour of materials under pressure, he was next able to extend his measurements to pressures of 50,000 atmospheres, and further apparatus is being developed in his laboratory for investigations to pressures of 100,000 atmospheres. Not only is the work of direct application to geophysics and other branches of science and technology, but also the investigation of the effect of pressure on the outer structure of atoms is of theoretical importance. Bridgman was awarded the Nobel Prize for Physics in 1946. He is not only a pioneer in this field of high pressure, but also has made important contributions to thermodynamical and statistical theory and has also influenced philosophical thought in the realm of mathematical logic.