The lowest limit of temperature obtainable by the hitherto usual method of evaporating liquid helium lies at about 0⋅7º. At this temperature the vapour pressure of helium is already so small that it does not seem possible to proceed to appreciably lower temperatures in this way. In the course of last year the first successful experiments in attaining still lower temperatures were carried out using the magnetic method proposed by Debye and Giauque. This method is based on the possibility of diminishing considerably the entropy of some paramagnetic salts by isothermal magnetization. The subsequent demagnetization, if carried out adiabatically, then results in a lowering of the temperature.