ALL physicists deplore in the death of Sir Arthur Eddington the passing of a great leader in their science, whose genius they acknowledge as freely as they admit, in many cases, their inability to follow him in his most daring and difficult advances. These particular advances, however, form only part of his life's work: certain of his most striking achievements are based upon bold and penetrating applications of simple physical conceptions to problems not contemplated when they were elaborated. Nuclei stripped of all their electrons—of their crinoline, as Sir Alfred Ewing termed it—are a simple corollary of the nuclear theory of the atom: the pressure of radiation, measured in the laboratory, had been invoked to explain the behaviour of the tails of comets. Eddington seized upon these conceptions and, combining them with the laws of gravitation, evolved a theory within the comprehension of the ordinary physicist, which explained beautifully the general features of stellar structure and stellar evolution. Bare nuclei, together with the electrons freed from their normal orbits, readily represent a gas of great density, such as was required to explain the compactness of the dark companion of Sirius and other white dwarfs. By bold imaginative conceptions of this kind, combined with technical mathematical powers of the highest order, Eddington made of the stellar universe a physics laboratory where somewhat extreme conditions prevailed, but nevertheless a physics laboratory.