able to raise or sink such that the overall weight will be counterbalanced by Archimedes' force; in 

 other words, so that everywhere the equation was satisfied 



h Siv — Sj ' 



where ^i = the ice density, 



6(y = the water desnity, 



s = the immersion of the in-the-water part of the ice blocks, 



h = the height of its above- water part. 



(1) 



Figure 99. The water line (mn) and the isostatic line {pr) in the vertical pass 

 of the ice field (diagram) . 



We shall call line pr , represented by a broken line in figure 99, the isostatic line. Referring 

 our considerations to the entire ice field, we shall receive the isostatic surface. It is clear that 

 everywhere where the isostatic line pr proceeds or passes higher than the water line, the isostatic 

 forces there operate, directed downwards; there, where the isostatic line proceeds lower than the 

 level of the sea, the isostatic forces are directed upwards, as is shown by the arrows in figure 99. 



At points where the isostatic line coincides with the level of the sea, we get an isostatic 

 balance. 1 call an ice formation isostatically counterbalanced at every point of which the isostatic 

 surface coincides with the level of the sea. 



It is assumed that there are not any ideally counterbalanced formations in nature. Fine devia- 

 tions do not have any significance, however, since the forces being created cannot be sufficient for 

 overcoming forces of cohesion (the equalization due to the flow of ice proceeds too slowly), but large 

 deviations quickly bring vertical movements of separate parts of the ice, which level or even the 

 balance. 



The isostasy phenomena acquire particular significance in summer, when the cohesion of parts 

 of the ice is weakened and when destruction of above-water parts of the ice proceeds particularly 

 disproportionally. Isostasy at this time is basically connected with two processes: hummocking, 

 and the flowing of water from the sneshnitsa (snow puddles) under the ice. 



Let us represent for ourselves a hummocked field isostatically balanced. If we may assume 

 that the above- and under-ice parts of the hummock consist of approximately equal blocks of ice and 

 that the spaces between the ice blocks are filled with air in the parts of the hummock over the level 

 of the ice and with water in the parts beneath the ice level and are located approximately systemati- 

 cally along the vertical with regard to the level of the sea; in other words, the coefficients of filling 

 are equal, on any vertical of an isostatically balanced field, the correlations between the height of 

 the ice hummock and its draught will be determined by formula (1) or by the 



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