On the mechanical possibility of the descent of glaciers, by their weight only

All the parts of a glacier do not descend with a common motion; it moves faster at its surface than deeper down, and at the centre of its surface than at its edges. It does not only come down bodily, but with different motions of its different parts; so that if a transverse section were made through it, the ice would be found to be moving differently at every point of that section. This fact, which appears first to have been made known by M. Rendu Bishop of Annecy, has since been confirmed by the measurements of Agassiz, Forbes, and Tyndall. There is a constant displacement of the particles of the ice over one another, and alongside one another, to which is opposed that force of resistance which is known in mechanics asshearing force .