434 R. WM. Deeley—The Structure of Glaciers. 
axes. The consolidation must also be facilitated by the slow melting 
of the points of contact of granule with granule, due to the lower 
melting-point of the more stressed portions. Time is therefore an 
important consideration, as also is temperature, in the process of the 
consolidation of snow consisting of a great number of ice spicules, etc., 
into glacier ice consisting of a much smaller number of large 
crystalline grains. 
The Antarctic Great Barrier, Professor T. W. E. David says, is 
composed of highly compacted snow rather than glacier ice. From 
measurements of the snowfall on it and the rate of flow he concludes 
that the ice at the depth of 900 feet at the Barrier face is only 
900 years old. As the visible face is only about 120 feet high the 
oldest ice seen is therefore 120 years. To what extent the snow has 
really been converted into glacier grains we are as yet unable to say. 
It, however, clearly contains a very large number of air bubbles 
which give it the appearance of compacted snow and much reduce its 
density. 
In most instances the névé surface is melted by the sun or warm 
air. In this way more or less impervious layers of ice are formed, 
which prevent the escape of the imprisoned air. 
One of the first impressions produced on the mind on entering an 
ice cave is the solidity and blueness of the ice. One, however, soon 
notices white discontinuous layers, generally roughly parallel with 
the glacier bed, but much twisted and broken. These are the 
stratifications produced in the névé by the imprisoning of air bubbles. 
Although the mass of the ice consists of glacier grains of all sizes 
and shapes the bubbles bear no relationship to either the size or the 
arrangement of the grains. The great majority of the bubbles are 
enclosed in the ice granules. Only occasionally are they seen at the 
interfaces. It would seem that as the crystals grow or decrease in 
size and the positions of the interfaces alter the bubbles are not 
displaced. 
It is only at great elevations, where ice falls from hanging glaciers 
and thus exposes fresh clean surfaces, or in ice caves that 1 have seen 
the regular stratification due to imprisoned air. In the mévé it is 
very clearly marked, but lower down in the glacier the differential 
motion, the opening and closing of crevasses, ete., give rise to great 
distortion of the white layers. 
Veining.—A careful examination of the walls of an ice cave will 
reveal the fact that the glacier consists of an agglomeration of ice 
granules, the outlines of the granules being clearly defined by the 
delicate lines on their surfaces or the melting along the lines of 
contact. If a thin piece of notepaper be placed against the ice and 
the surface of the paper be rubbed with a pencil a rough copy of the 
surface markings is obtained. The granules vary in size very much, 
the glacier being composed of beds of granules of varying coarseness. 
In a paper communicated to the Guonocicat Macazrye by Mz. G. 
Fletcher and the author we say ‘‘the veining resulted partly from 
the arrangement of the crystal grains and partly from a variation in 
the shape of the grains and partly from variations in their 
dimensions ”’ 
