THE FLOW OF GLACIERS 45 



weight of the ice is sufficient to account for its movement, 

 and that a mass of lead corresponding to a glacier would 

 in the same position move much as it does. The close 

 fitting of the glacier to its bed, the fusion of tributary 

 glaciers with a larger one, and the more rapid movement 

 of the middle part of a glacier than of its sides (which are 

 arrested and slowed down as is the water of a river by 

 friction with the rocky sides of its bed) are due to the 

 continual cracking and breaking with constant regelation 

 of the ice at all points where it is strained or subject to 

 tension. Regelation gives it, in the gross, the properties 

 of a viscous body, such as pitch or soft sealing wax — 

 although ice is certainly, when small bits or crystals of it 

 are examined, or even when we deal with a block of it 

 weighing a ton — not a viscous body capable of being 

 extended, that is, elongated or widened in shape, by 

 pulling. It is not capable of being drawn out into strings 

 or threads as are viscous bodies like pitch, sealing-wax 

 and thick treacle ! Under pressure, however, it does behave 

 like a viscous body, and fragments or powder of ice can 

 be squeezed in a mould into a solid coherent mass (as one 

 can squeeze and fuse powdered wax or amber when warm), 

 owing to its property of "regelation," that is to say, of 

 partial thawing under pressure and immediate re-freezing 

 when the pressure is relaxed. 



The thick, sticky " flows " or slowly moving streams of 

 mud or watery clay, which one may see at the base of 

 sea-side cliffs in many places, for instance, the Isle of 

 Wight, are in important respects like small models 

 of glaciers. One sees in them clearly enough that the 

 middle part flows more quickly than the sides, and 

 one sees the formation of crevasses by the "tearing" 

 of the unequally moving mass. And the formation 

 of what is called the veined structure of a glacier 

 and of dirt bands on its surface are illustrated by similar 



