THE ICE. 251 



previous chapter ; these icebergs then, frequently and 

 accurately observed, may be accepted at least pro- 

 visionally, as a substitute for the investigations to be 

 made on land, concerning the transformation of snow 

 into glacier ice. 



All Antarctic travellers have been struck by the 

 peculiar stratification of the icebergs, which with newly- 

 formed bergs runs in parallel horizontal lines with the 

 upper surface. These strata, consisting of snow-white 

 and deep cobalt-blue ice, alternate from top to bottom, 

 but they are not of uniform thickness ; at a great eleva- 





Iceberg seen on 23rd February, 1874 (from the Challenger's Reports). 



tion above the sea-level, near the surface of the berg, 

 the still undulating white strata are some four feet thick, 

 the blue strata being comparatively very thin ; but, as 

 we descend lower down, the white strata diminish and the 

 blue increase in thickness, till, with a berg about eighty feet 

 high at a distance of sixty to seventy feet from the surface, 

 the white strata measure only one foot or so in thickness, 

 and at last disappear altogether, so that the mass below the 

 surface of the water consists almost entirely of ice that 

 is perfectly blue and transparent. An original experiment 

 made by the Challenger supplies satisfactory information 



