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5. According to these conceptions, there cannot exist any magnetic flux 'frozen' in the interior of pure supraconductors ; a permanent flux should only be found confined to the hollows of supra-conducting rings. The topological connectivity of a supraconductor, therefore, is a property extremely characteristic of its behaviour: the multiplicity of its connectivity, diminished by one, immediately indicates the number of independent conservative quantities, that is, of independent invariant magnetic fluxes.