188 Fr^ank Carney 



mass of snow increased, and by its own pressure the lower parts 

 were changed to granular neve. With the increments of later 

 seasons, granular ice was formed; with continued snowfall, 

 this moved laterally as glacier ice. 



How glacier ice 7noves. Should you visit a valley glacier of Swit- 

 zerland you would find in its neve field evidences of growth, while 

 at the low^er terminus of the glacier you would see evidences of 

 wastage. Between these two points the valleys generally have a 

 marked slope. The question of motion does not here appear to be 

 complex. Ice, we all know, is not a solid; a block of it, when 

 supported only at the ends, sags in the middle of its own weight. 

 The movement of these valley glaciers is so obvious and so natural 

 that they are sometimes called ice rivers. It is immaterial how 

 deep they may be; a tongue of ice in a valley, which slopes away 

 from a mountainous area, should move. 



But when we think of a great continental glacier, covering thous- 

 sands of square miles in one continuous sheet, we cannot find the 

 same reasons for motion. Motion in Alpine glaciers appears to 

 be largely a matter of gravity, and yet the process is not the same 

 as the motion of a cable, which is being fed through an inclined 

 conduit, or what occurs at the lower end of an inclined plane, 

 already filled with ice blocks, when we add another block to the 

 upper end. While there is movement in these Alpine glaciers and 

 in the ice sheets, they do not appear to move as a unit ; the motion is 

 not so simple. The gathering or dispersion center of an ice sheet 

 is its place of growth, the margin, its place of decay. When the 

 margin remains stationary, as well as when it advances, a forward 

 motion must prevail in the ice, back to the dispersion area, and this 

 in spite of a prevailing temperature below the melting point. 



Ice is a mineral ; when forming, the molecules arrange themsel- 

 ves according to the hexagonal system of crystals. When snow- 

 flakes are piled up, these crystals are bent of their own weight, 

 crowded together, interlocked, and they suffer some melting. It 

 is thus that the structure of neve becomes granular, and the indivi- 

 dual granules grow. By experimentation, it has been proved that 

 these granules grow under all conditions of temperature. We all 

 know that in crystal growth great pressure is exerted ; thus, jars 

 are broken when water freezes in them. The expansion causes 

 pressure, and because of pressure, great tension must exist in 

 ever}' ice area. Physicists teach us that heat is an accompaniment 



