The discovery of superconductors by Kamerlingh Onnes in 1911 was immediately followed by the suggestion that they might be used for generating intense magnetic fields with a relatively low expenditure of energy. Practical difficulties, particularly the fact that the earliest materials lost their superconducting properties in quite small magnetic fields, resulted in no useful progress then being made. Quite recently, however, the discovery of superconductors having different properties has made feasible superconducting magnets producing a field of as much as 100 kilogauss. © 1964.