The air content fluctuated from 7 to 15 per cent in the icebergs investigated by Barnes near 

 Newfoundland, and, as an average, was about 10 per cent. 



The density of the icebergs fluctuates, according to Smith, from 0.6 to 0.92, in accordance 

 with their air content. 



The most porous and light glacial ice forms at very high latitudes. This ice is very lightly 

 fused and falls apart easily. Icebergs consisting of such ice are called "sugar" by the Norwegians. 



The copious release of air bubbles which is usually observed during the melting of glacial 

 ice, and which is accompanied by characteristic hissing resembling the hissing of frying fat, should 

 evidently be explained by the increase of pressure in the air bubbles trapped in the ice. 



The density of porous ice is determined by the formula 



S = S„(l-4), (3) 



where dg is the density of ice without air bubbles, and n is the porosity of ice. 



The density Sq is a function of the temperature and salinity. As we saw in table 46, under 

 natural conditions it fluctuates within the limits of 0.920 to 0.953. 



From formula (3) we obtain 



n = 100 



i^-^y <*' 



I computed the porosity of pure ice and snow as a fimction of its density (table 50) according to 

 formula (4) . 



TABLE 50. THE POROSITY OF SNOW AND ICE AS A FUNCTION OF DENSITY 



Density ...0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

 Porosity ... 89 78 67 56 46 35 14 13 2 



LITERATURE: 8, 9, 13, 44, 62, 115, 12&. 



Section 67. Buoyancy 



Only a comparatively small part of ice rises above water (figure 58) as a result of the slight 

 difference between the densities of ice and water. 



Let the density of ice be 6 , , and density of water 6^, , the above-water volume F^ , and the 

 underwater volume V , then according to Archimedes Principle, between these quantities there 

 exists the relationship; 



169 



