Actually, the heat of crystallization released during ice formation must immediately be re- 

 leased to the atmosphere for the process to continue, since otherwise it will be used in raising the 

 temperature of the layer. Hence, it is most natural that the growth of the nuclei develops primarily 

 in a horizontal direction and, due to this, prismatic crystals are formed first whose optic axes are 

 parallel to the terrain of freezing. Further, in the cells between them, according to Golovkov's 

 microscopic experiments , plate crystals developed whose optic axes are perpendicular to the plane 

 of freezing. From the moment the possibility of further horizontal growth of crystals is halted by 

 contact with adjacent plates, a growth of vertically oriented crystals begins to predominate. This 

 process is disrupted only when separate rapidly developing vertically oriented crystals turn on 

 their sides. 



As a result, we obtained ice which resembles a fusion of trxmcated prisms and pyramids 

 which face upward and whose form more or less approximates a hexagon, and whose cross section 

 slowly decreases downward. 



Inasmuch as the ice crystals consist only of water molecules, all impurities gradually pass 

 from the water into the interlayers between the crystals. The basic mass of a salt solution, due to 

 its great density, runs downward, while air bubbles are forced out by the continuing growth of the 

 crystals. Thus, when water is in a calm state and is gradually cooled, a pure surface ice of needle 

 structure, free of impurities and air bubbles, is formed. 



The needle structure of ice is most clearly evident, e.g. , in ponds during spring, when 

 melting begins. Solar heat is absorbed mainly by the salts and slime inclusions contained between 

 the layers surrounding the individual crystals. As a result, the lower surface of this ice appears 

 honeycombed, as if it had been peppered with sharp barbs, that is, crystals of pure ice separated 

 from each other by films of melt water containing slime and salts. 



Needle ice, as we have seen, is formed under the condition that the water is at rest. But if 

 the water is sufficiently agitated, ice forms in a somewhat different manner. Actually, the super- 

 cooling of water which is necessary in this case, for the creation of nuclei of crystallization, can 

 appear in the entire volume of the agitated liquid, and then ice formation will begin around the 

 formed nuclei. The released heat of crystallization is carried off to the surface by the eddies 

 which form during the agitation, and these same eddies constantly bring supercooled water particles 

 from the top, which according to Altberg, guarantees further development of the process. Thus, if 

 ice formation in still water always begins at the surface, with sufficient agitation of the water, ice 

 formation can begin at a certain depth, or even near the bottom. For this, the essential factors 

 (according to Altberg) are: water in the state of motion (the dynamic factor) and supercooling it 

 (the thermodynamic factor) . 



Because of their small size, the ice particles which form within the mass of water do not 

 float to the surface immediately, but are carried from place to place, freeze together on contact, 

 and finally rise to the surface. During the formation of deep ice, the water ordinarily contains 

 myriads of ice particles throughout its entire mass which are barely visible; they appear as shining 

 dots when the observer sees them at a certain angle to the sun's rays. It is noted that when a small 

 piece of ice is introduced into supercooled water, a certain clouding of the water occurs at first 

 which is called ice fog. Then, tiny ice particles, which are true colloids, collect into bunches, 

 grow, and finally turn into a spongy mass saturated with water. 



According to Altberg, who formulated the above theory of deep ice formation, the elementary 

 particles of this ice are perfectly round discs with mirror-like side surfaces and an even, as it 

 were, polished, rim (figure 30). This form of deep ice elements is explained by the melting and 



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