Edinburgh, Cambridge, and Baffin Bay

Abstract

My postgraduate work started in 1930 in Edinburgh with Professor C.G. Barkla on the scattering of X-rays. A primary goal was somehow to win acceptance by Lord Rutherford for work in the Cavendish Laboratory, Cambridge. Being interested in instruments, I spent much of my time perfecting the gold-leaf tilted electroscope of C.T.R. Wilson. Eventually I produced a very quick-acting, critically damped quartz-fiber**electroscope with sensitivity limited only by the Brownian motion of the fiber (Carmichael, 1934). Ionization pulses from individual alpha particles could be observed at response times of a fraction of a second and the fiber could not be damaged by being driven off scale towards the plate. As regards the latter feature, Wilson told me later, at Cambridge, that the tilted electroscope had provided him with a portable instrument for his outdoor work. By charging the plate of the electroscope to a high voltage, the instrument could be carried safely because “the leaf remained steadily pointing towards the plate which it was just too short to touch.”