As a slight contribution to the elucidation of questions of denudation, and at the same time an exemplification of the application of mathematics to a geological problem, I send the following:

Noticing a lofty chalk cliff, forming the face of an old quarry in the neighbourhood of Lewes, I remarked that the action of the weather upon the surface was to disintegrate it equally all over, so that the face of the quarry remained vertical, while the stuff that fell down formed a talus, whose surface was approximately a plane, inclined to the horizon at that particular angle at which such materials will stand. The question then occurred to my mind— What will be the profile of the solid chalk behind the talus?.