Popular interest in the progress of physical science has increased very rapidly in the last few years. Perhaps the spectacular ‘mysteries’ of wireless and the intriguing paradoxes of the theory of relativity are the chief causes. For every home now has its Magic Box—a piece of pure physics; there is not a familiar thing in it, not even that sine qua non of all things that ‘work’—a wheel, only mysterious parts called condensers, grid-leaks, inductances, and thermionic valves. And surely, when a Sunday newspaper produces a facsimile page of Einstein’s recent paper in German containing abstruse tensor equations, reverence for the mathematical physicist is nearing its zenith.