In glaciated regions I have several times encountered an aberrant and puzzling type of sculpture. Inclined surfaces, so situated that they can not have been subjected to postglacial stream scour, are sometimes carved in a succession of shallow, spoon-shaped hollows, and at the same time are highly polished. They resemble to a certain extent the surfaces sometimes wrought by glaciers on well-jointed rocks, where the hackly character produced by the removal of angular blocks is modified by abrasion; but they are essentially different. Instead of having the salient elements well rounded and the reentrant angular, they have reentrants well rounded and salients more or less angular; and they are further distinguished by the absence of glacial striæ.
An example appears in the foreground of plate 40, representing the canyon of the South fork of the San Joaquin river, in the heart of the glaciated zone . . .