JAGGAR: EROSION AND SEDIMENTATION. 303 
believed by the writer that bevelling of divide surfaces to produce even 
sky-lines has been frequently confused with planation in works on 
geomorphology. Planation, where it is not marine, requires a flood- 
plain. (See Gilbert, G. K., 1880, p. 120.) True fluviatile planation 
is due to lateral corrasion and the test for it is the presence of facetted 
surfaces across diverse structure, where glaciation or marine planation 
are positively absent. It is to be hoped that the complex mechanism 
of planation may some day be subject for the experimental method. 
