Glacial Erosion in Norway. 219 
flat, sometimes sloping steeply—they adhered by friction, and by 
the pressure of the superincumbent weight. Although held in the 
ive on four sides, with a force pushing. downward, the viscosity of 
TAF W 
HA | 
i 
a .—Section of Fondalsbreeen, a, bed rock; c, cavern under glacier 5; d,loose 
ne; f, groove under the ice. 
the ice, or the resistance of its molecules in disengaging themselves 
from each other in order to flow, was less than that of the friction 
between the loose stones and the rock ; consequently the ice flowed 
around and over the stones, leaving long grooves upon the under- 
surfaces of the glacier. The first observation made was at Fondals- 
breen (Fig. 1), where an angular stone (Fig. 1 d) whose section was 
ten by eighteen inches, rested upon the sloping face of smooth rock 
(a). For twenty feet below the stone, the under-surface of the 
glacier was grooved (f) by the moulding of the ice about the 
obstacle. This distance showed the advance of the glacier after the 
stone had come in contact with the rock, for it had evidently been 
Completely buried at the lower end of the groove, before the ice 
had begun to flow about it. As the ice between the stone and the 
tock gradually disappears, the embedded stone does not suddenly 
cease to move, but drags, until enough of the surface rests upon 
the rock to allow of friction between the two granitoid surfaces to 
Overcome the viscosity of the ice, when the latter flows around the 
obstacle. Elsewhere, an example was seen of this action, The 
knife edge of a wedge-shaped piece of gneiss was pr i 
beneath the ice and resting upon the rock. The front end of this 
stone had moved beyond the subjacent surface, while the posterior 
