50 Chemical and Physical Notes 



were dependent only on the lowering effect of pressure on the 

 melting-point of pure ice, it would be difficult for such a mass 

 of ice to start when it arrives at an outlet. The impurity of 

 all natural water, and the effect which it has in lowering the 

 melting-point of ice at ordinary pressures, remove this diffi- 

 culty. However compact and solid the blue ice may look, 

 there will always be some brine between its grains which will 

 permit some yielding of its mass, which in its turn will 

 produce a first generation of heat ; this will produce a further 

 yielding, and in due course a further generation of heat, and 

 the effect of this initial agency, when combined with the 

 powerful effect of fusion and regelation under conditions of 

 very slight variations of pressure, is the extraordinary rate 

 of motion observed in the glaciers of Greenland. 



It has been pointed out that the whiteness of the surface 

 of a glacier is due to what may correctly be termed sun 

 burning or sun weathering. The icebergs which are met with 

 at sea have an equally white surface ; but where the interior 

 is exposed, either in crevasses or in caves melted out by the 

 waves, the deep blue colour of the fresh ice is visible. It is 

 obvious that the whole of .the surface of the glacier which is 

 immersed in water at greater depth than that to which the 

 sun's rays can penetrate must have the same blue colour, and 

 it is equally obvious that when an iceberg turns completely 

 over, it must stand out as an intensely deep blue mountain of 

 ice among the multitude of sunburnt white ones. On one of 

 the fine days during the sojourn of the "Challenger" in 

 Antarctic waters, a striking and magnificent example of this 

 was observed, but the cause of the blueness of the strange 

 berg was quite unsuspected. If ice were collected by bombard- 

 ment or otherwise, from such a berg, the grain would be large 

 and well developed, and the ice would be quite compact and 

 free from vesicles. In the region visited by Dr Arctowski, 

 the glaciers and the icebergs were comparatively small and of 

 an Arctic character. The distribution of snow, n<?ve, and ice 

 he describes as being similar to that in the Alps at a height 

 of 3000 to 4000 metres. There appeared to be very little 

 melting, yet the glaciers advanced steadily towards the sea. 



