VEGA-EXPEDITIONENS VETENSKAPLIGA AIIBETEN. 311 



would be among the first to separate from tlie cooled sea-water 

 already at — if.i C. This agrees well with the table 1, of this 

 chapter, which shows, that of all the constituents of the sea- 

 water the brines are most deficieiit in Na^O and SO3. The 

 percentage of sulphuric acid in ocean water is about O.2228 

 (calculated as SO3). Suppose all this to combine with its equi- 

 valent of Na-iO and freeze out as a cryohydrate in the ratio 



[0.3954 % NasO^SO^ + 8.3947 % H2O] + 91.3... % aq. 

 (cryohydrate) ^ (ice) 



then 8.69 % of the frozen sea-ice onglit to consist of the solid 

 cryohydrate of Na2S04 instead of pure ice with a few dröps 

 •of concentrated brine, as is ordinarily assumed. It would be 

 impossible to explain, how an amount of O.3954 % of foreign 

 matter could so essentially modify the physical properties of 

 the ice, as is seen in the foregoing chapters, if the substance 

 was included in the ice as solid crystals or as adhering dröps 

 of brine, hut we Avill have no difficulty to admit, that the 

 presence of 8.69 % of a solid cryohydrate, which physicalh^ 

 and chemically is a different body from the pure ice, can 

 modify its properties considerably. Moreover this solid has 

 its melting point at — 0°.7 C. Consequently it will endure in 

 the solid state as long as the ice itself Other cryohydrates, 

 as for example MgS04, MgCl-i, CaClo, Na Cl, which arise at 

 lower temperatures, will consequently melt again long before 

 the rest of the ice. Therefore every rise of temperature will 

 promote the metamorphosis of the ice extraordinarily. The 

 ■cryohydrates of the chlorides will liquefy and escape, if any 

 chance is left to them. This is realized by the abnormal 

 contraction of the sea-ice by the fall of temperature, which 

 <?auses a strain and a bending on its surface, which finally 

 ends with its bursting and breaking up into remnants and 

 fissures. ^ When the temperature rises again, the liquefied 



1 The reader will of course perceive, that I do not mean to say, that 

 the sulphuric acid of the sea-water freezes out at once as a cryohydrate at 

 — 0.°7 etc. but that I only wish to give an idea of the whole, very compli- 

 cated, process by the chosen example. 



^ The uppermost layer of the ice, having acquired the temperature of 

 the air. will begin to assume the j)roperties of a härd body and contract its 

 volume (while the next layers, to which the atmospheric cold penetrates 

 more slowly, is still expanding) and consequently breaks up into innumer- 

 able rifts. In short I believe, that the regular expansion or contraction 

 seldom causes any violent dislocation of the ice. Such effects are due to 

 the great abnormal changes of volume, which take place in fresh-water ice, 



