194 



PRINCIPLES OF STRATIGRAPHY 



arated out in the above order, sodium sulphate first and calcium 

 chloride last. Owing to the presence of the other salts in sea water, 

 however, Na^SO^ does not separate out at its eutectic temperature 

 of —0.7°, but only at —8.2°. When the entire mass is frozen, a 

 mixture of ice and salt crystals results, the so-called cryohydrate, 

 which may be compared with graphic granite (pegmatite), the best 

 known eutectic among rocks. The following table shows the results 

 of Ringer's experiment in freezing 1,000 grams of sea water of 

 35.05 permille salinity ( Krummel-20 150^ ) : 



At temperature of . 



-5^ 



-8.2= 



-15° 



-23° 



Liquid remains, grams 



Solid occurs, mostly ice, in grams . . . . 

 Solid Na2S04 in grams in above solid . 



429 -5 



570.5 



0.0 



281.5 



718.5 



0.0 



234.0 

 766.0 



1.84 



186. 1 



8139 

 3 09 



134-9 

 865.1 

 3-68 



Temperatures lower than —8.2° C. exist in the drift ice itself 

 near the surface (at depth of 40 cm.) from October to May in- 

 clusive, falling close to —24° in January. At a greater depth the 

 temperature is invariably higher in the cold months and lower in the 

 warm. Thus at 200 cm. depth the January temperature, which at 40 

 cm. was —23.9°, was —10.6°, while the July temperature, which at 

 40 cm. was — 0.5°, was at 200 cm. —1.4° C. In all cases the ice in 

 winter is warmer than the air above it. The water, however, retains 

 a nearly constant temperature of —1.5° to —1.7° C. From the above 

 considerations it appears that sea ice is likely to be richer in sul- 

 phuric acid (SO3 -|- H2O) than normal sea water, while sea water 

 coming in contact with ice at a temperature below —8.2° C. will 

 have its SO3 extracted and so become poorer in this substance. On 

 the other hand, portions of the ocean where the sea ice melts will 

 be richer in SO3 than normal sea water. The normal, according to 

 Dittmar, is 11.576 parts of SO3 to 100 CI; according to Forchham- 

 mer, it is 11.88; and, according to Schmelck, it is 11.46. Pack ice 

 melted by Irvine gave 10.84, ii-97' ^nd 11.93 foJ" different samples, 

 two of them higher than the highest figure for normal sea water. 

 One piece of ice melted by Hamburg gave a proportion of SO3 of 

 57.4 or 5 times as much as normal sea water. This, however, had 

 only 0.05 permille of chlorine. 



Range of Temperature of the Oceans. The annual range of 

 temperature of the waters is of greater bionomic significance than 

 the absolute temperature itself. Sir John Murray has mapped these- 



