In part I, the magnetic after effect of cold rolled iron is studied both by semi-static and dynamic measurements. It is verified that: the static after effect in a weak field and the so called Jordan's constant are not observable in contradiction to Schulze's measurements. But the after effect is observable in the range of irreversible magnetisation. The after effect of iron, annealed after being cold rolled, is also investigated. The after effect in the range of initial permeability becomes observable in a recrystallised state, in agreement with Schulze's results. In addition it is found that the part of loss angles, observed at low frequencies, attributable to the macroscopic eddy currents is larger than the theoretical value. It suggests the existence of a relaxation due to another origin which has not been taken into account in the analysis of loss angles. Hence, in part II, the measurements of apparent permeability at higher frequencies are carried out for the cold rolled iron. The time of relaxation...