PROF. W. M. THORNTON, of Armstrong College, Newcastle-on-Tyne, took as the subject of his inaugural address, given to the Institution of Electrical Engineers on October 25, the electrical properties of insulating materials. He said that there is much in the advanced electrical science of to-day that can never come into practice, yet in the maze of experimental research and wave mechanics which constitute modern physics, there is hidden the ex planation of some of the outstanding problems of electrical engineering. Industry is impatient and has to advance without waiting for the slow formulation of fundamental theory. As a result, the insulation engineer in the past found himself responsible for vast expenditures, with little but empirically gained experience for his guidance. In these circumstances, it is not surprising to find that in many respects it is the problem of electrical insulation that is holding back the fullest development of high-voltage en gineering for the transmission of large blocks of electrical power. There is at the present time no theory of dielectric behaviour that covers all the facts. Yet there seems to be behind the phenomena a hidden simplicity at least as simple as the free-electron theory of conductors. For example, it has been shown experimentally that the electric strength of air is in fact a physical constant comparable in accuracy of determination with most of the constants of Nature. We know also that all insulators break down at a lower voltage when the frequency of the field is raised. Prof. Thornton showed some beautiful experiments to illustrate that dielectrics obey simple laws. The nineteenth century was the age of the machine. Perhaps the twentieth century will be regarded as the age when insulation was made perfect.