VEGA-EXPEDITIONES S VETENSKAPLIGA AhBETEN. 321 



The numbers found in the experiments V & VI of table 2 of 

 this cliapter can not be substituted for R, because these deter- 

 minations were executed at temperatiires 6 or 7 degrees lower 

 than T' and the latent heat is calculated for 1 kgr. of the salt 

 water examined, without deduction for that part, which must be 

 enclosed as unfrozen brine, in case the temperature at the free- 

 zing was so high as T'. Besides we have hitherto supposed 

 the whole process to be a regular cyde, where every alteration 

 represented by the fractions ^ , il . . . ^ , ^i_ . . . , is reversihle. 



From this there will in reahty be found to be several excep- 

 tions, since many phenomena connected with the freezing of 

 sea-water, the overcooling etc. . . are not of reversible nature, 

 and the evaporation, which constantly takes place from the 

 water and the ice, gives rise to a series of thermoJynamic 

 processes, which doubtlessly are of influence upon the move- 

 ment of the ocean, hut fall entirely beyond the reach of the 

 present discussion. 



Nevertheless it seems probable from the general outlines 

 of the phenomenon, which I have endeavoured to sketch in 

 the foregoing, that the transport of the warm water across 

 the ocean to high latitudes need not to be attributed solely 

 to external forces, since the melting and freesing of sea-ice is 

 found to involve the possihility of a transformation of thermic energy 

 inf o mechanic force. 



If we admit the possibility that by the peculiar conditions, 

 under w'hich the melting and freezing of sea-water takes place, 

 a certain quantity of solar heat is made useful for mechanic 

 [)urposes, it can not be difficult to understand hotv the melting 

 of ice in sea water can give rise to an ocean current. Professor 

 Ekman in liis paper upon the origin of currents ' has proved 

 that this must be the etfect of the melting, as follows: 



Suppose a bit of pure ice, which swinis freeJi/ in salt water, 

 to melt and the liquefied ice to retain its former place, then 

 the level of the fresh water will stånd higher than the sur- 

 rounding sea, on account of the greater spec. volume of the 

 fresh water. This makes it expand above the surface of the 

 salt water. Pure ice, melting in pure water, occasions no 

 current, because its spec. volume is equal to that of the sur- 



rounding fluid. — If we pursue the subject further, wc 



find, that the sea-water in the moment of freezing must perform 

 a certain amount of ?vorJi, by raising a part of the ice above the 



1 Öfvers. K. V. A. Förb. 1875. N:o 7. 



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