Crevasses, caused by strains from variations in the rate of motion of different parts of the glacier and convexities in the channel, are mere cracks when they first open, so narrow as hardly to admit the blade of a pocket-knife, and gradually widen according to the extent of the strain and the depth of the glacier.

Huge overhanging cliffs are to them steps within the reach of human legs; yawning crevasses are ditches to be jumped; and foaming waterfalls are like streams from penny squirts.