Sverdrup gave Makarov extremely interesting and valuable information. During the third 

 winter, a fissure was formed under the strip under the Fram . The fissure closed sometimes and 

 at other times opened. As soon as the fissure opened, lumps of significant size began to float out 

 from below. "This shows, " says Makarov, recalling his conversation with Sverdrup, "that many 

 lower lumps constantly travel. The current of the water and the movement of the ice change their 

 direction so that if the migrating ice block stops under certain conditions, under others it can move 

 from the spot. " 



It is clear or comprehensible that such traveling blocks falling under ice with a small thick- 

 ness stop, and possibly freeze, and, in such a way contribute to the general equalization to the 

 thickness of the ice. 



It is necessary to add that the lumps which compose the under-ice part of the hummocks are 

 not only transformed but are also gradually destroyed. 



Let us assume that a strong and cold ice block is driven under the ice. From the beginning, 

 it increases somewhat in its dimensions, owing to its low temperature, but after that, as the 

 temperature of the ice block becomes equal to the temperature of the surrounding water, it grows 

 crumbly and begins to disintegrate into component parts and begins to melt. The tidal currents 

 have particular importance in this relation for the ice, which is immobile; but for floating ice, it is 

 wind drift. The under-ice parts of the ice of the hummocks, parts which are produced below, are 

 subjected to an interesting ablution by the water, which moves with a velocity different from that of 

 the movement of the ice fields. 



The model test, carried out by Makarov, is interesting and simple for the exposing of the 

 influence of moving water in the destruction of ice. 



Two pieces of ice approximately equal in weight were placed simultaneously into two tubs 

 filled with water, with a temperature of about -1.2°. In the first tub, where the water was at rest, 

 the piece of ice decreased in weight 6 per cent in a period of 3 hours; in the second, where the 

 water, supplied from the bottom, circulated continuously and poured out over the rim, the ice de- 

 creased 50 per cent in the same amount of time. 



The results of this test become clear if we recall the analyzed conditions in Section 62 of the 

 balance of the system of ice in water. Owing to the phenomena which has been pointed out, the 

 under-ice parts of the hummocks are all more destroyed with the course of time and the stress of 

 the over-ice parts of the hummocks increase correspondingly. 



It is necessary to add to this that newer and newer snow drifts are noted along every hummock 

 in the course of time. 



If through determination of the dimensions of over-ice parts of hummocks are made, there are 

 less determinations of the form and deepening of the under-ice parts. 



At the time of his voyage with Makarov on the Ermak, Islyamov carried out measurements of 

 the depth of the hummocks with a Thomson tube. Makarov cites the results of several such measur- 

 ings in which the largest of the hummocks was equal to 13 m. 



As Makarov points out, "It is necessary to assume that the Thomson tubes [ during their 

 broaching or piercing under the ice under the hummock fields ] show passage in the ridges of the 



273 



