The cumulative effects of travelling bubble cavitation tend, in general, to pass through a maximum when the extent of nuclei is increased, the maximum being a function of the undesirable effect considered. It may be that this phenomenon of formation of patches becomes so significant that the blades get totally covered by vapour and that by successive degradation, the bubble cavitation transforms into and acquires the characteristics of a cavity cavitation. Travelling bubble cavitation on a hydrofoil at small incidence is, undoubtedly, one that poses the least problems in extrapolation; also, with respect to the conditions of its appearance, their effects in a developed state should pose no difficulty. This type of cavitation has been the subject of a number of experimental studies. It can be seen that pocket or cavity cavitation may also be encountered in the trailing zone of a hydrofoil at a small angle of attack but disappears as soon as some nuclei are injected.