Since the time of Agassiz, 1840, the Unteraar Glacier has maintained its rôle as a focus of glaciological research for mapping, seismic sounding, glacier movement, and hydrology. Variations of the velocity of the Unteraar Glacier with ice thickness and time are presented and discussed. The new map of the Aletsch Glacier at the scale of 1:10 000 enables the author to demonstrate the extent to which detailed mapping of the surface features of a glacier facilitates the study of surface velocity.