This paper deals with magnetic effects in metals cooled from above the transition temperature to below the superconducting temperature, while in an applied magnetic field. Previous work of Meissner and Ochsenfeld indicates that at the superconducting temperature the effective permeability of the metal became zero. It is found, however, that the effective permeability is greatly influenced by the composition and geometrical shape of the specimen. There is also, in general, a reduction in flux on removing the magnetic field after the superconducting temperature has been reached, but on re-establishing the field the flux through the specimen remains unchanged.