For hillslopes, the relationship of form to processes depends on the extent to which processes are able to fashion hillslopes in accordance with their capacities for sediment transportation. Gilbert (1877) made a distinction between those situations in which the rate of weathering limits surface degradation and those in which it is the conditions limiting transportation that determine the rate of degradation of the land surface. More recently, this distinction has been used to dichotomise hillslopes into those on which processes are weathering-limited and those on which they are transport-limited (Carson and Kirkby, 1972, pp.104-6; Selby, 1982a, p.199). Such a dichotomy is unwarranted for it both implies that so long as weathering processes yield an ample supply of transportable particles transportational processes will always operate at capacity, and denies the possibility of active erosion by hillslope processes.