Formula (5) gives an idea of the average thickness under the condition that the given region 

 is completely filled with ice; in other words, under the condition that the quantity of ice in this 

 region is 10 marks. With the thinned ice we receive a more general formula from formula (5) 



where n = the average quantity of ice in marks or points. 



Along with the idea of the average thickness of the ice, the idea of the average amount of 

 ice in the basin or of a part of it rises by which we agree to understand the proportion of the 

 actual area which is covered by ice (taking into consideration the measuring point system) to the 

 general area of the examined part or 



where q = the area occupied by the ice, 



n = the average marks of the ice, 



q = the general area of the examined region. 



It is clear that the average iciness does not completely characterize the thickness of the ice. 



Combining the ideas of the average thickness and iciness of the region, we receive the 

 average power or force of the ice cover according to the formula 



I was assuming the derivation of these formulas that both the level as well as the hummock 

 formations on any vertical are isostatically balanced and consequently the areas occupied by the 

 above and under ice parts of the hummocks are equal. 



LITERATURE: 41, 42, 77. 



Section 105. Decrease in the Area of Ice with Hummocking 



During the observation of the change of the area of ice on the White Sea and the reaction of 

 the wind, the large areas of clear water, opened after each ice hummocking, surprised Somov and 

 myself, and we made an endeavor at an approximate calculation. 



Let us assume that a cut of the ice field in the direction of the wind is represented in figure 

 103; in other words, in the direction perpendicular to the direction of the ridges of the hummocks. 

 In the figure, 



L = the length of the ice field before the ice hummocking, 



H = the length of the ice field after the hummocking process, 



a = the length of the hummocked part of the field, 



285 



