The excavation of a tunnel by I’Energie Ouest Suisse (EOS) presented inter alia the opportunity to construct a longitudinal profile of the glacier speed and also to observe the speed of the transverse contraction of a circular section. The swift change of shape without fracture was noteworthy. A second tunnel driven from the glacier snout straight up the subglacial stream gave the opportunity to establish a definite connection between the form of the glacier sole and its surface. Finally, measurements of the glacier speeds on the surface and their variations from year to year gave a closer indication of the nature of Forbes’s bands.