464: O. D. von Engeln — Studies on Ice Structure. 



molecules (water) developed in the crystal structure would, 

 owing to high reaction velocities, readily change back to the 

 solid phase and thus preserve the ice clear and coherent 

 throughout. 



The lower molecular cohesion of ice masses along the con- 

 tact planes of adjacent crystals, as indicated by the lower 

 crushing strength, suggests that such internal liquefaction as 

 occurs under non-uniform pressure may be localized between 

 the crystal units and also between the basal plates of the single 

 crystals. Such a deduction is corroborated by other evidence, 

 and this leads to some very interesting conclusions regarding 

 the structure of ice aggregates. These can best be presented 

 by first considering the premises on which they are based. 



Practically all natural waters carry considerable quantities 

 of dissolved mineral salts. It is. to be expected, therefore, that 

 such material will be to some extent incorporated in ice formed 

 on ponds, lakes and rivers. In large part, these soluble min- 

 eral salts in land waters are leached from rock substance. In 

 the case of glacier ice, however, there is little or no opportun- 

 ity for the incorporation of such material if it must be derived 

 from rock leaching. But one of the commonest soluble salts, 

 sodium chloride, in natural waters, is for the greater part not 

 derived from rock leaching but is carried by the wind during 

 storms as fine dust particles from the ocean and local salt 

 deposits to points remote from its origin. The difficulty of 

 accounting for the chlorine in inland waters and the well-known 

 excess of chlorine in the ocean are the facts responsible for 

 investigations that have shown, e. g., that in England at Ciren- 

 cester an average annual deposit of 36 - l lbs. of sodium chloride 

 has been for 26 years brought by the wind to each acre of sur- 

 face. Hence there is no difficulty about the incorporation of 

 a considerable quantity of this salt in glacial ice. Moreover, 

 it is suggestive that the regions of present day notable glacia- 

 tion are almost without exception favorably located for receiv- 

 ing supplies of wind-borne salt, directly from the ocean, from, 

 saline basins and from the surface of sea ice. 



An aqueous solution of sodium chloride will completely 

 crystallize at its eutectic point, — 22°C, forming what, has 

 been termed cryohydrate, a mixture of salt and ice crystals, 

 each distinct, in the proportions 23*5 per cent NaCl and 76 - 5 

 per cent H 2 0. If the solution is originally more dilute than 

 these percentages the excess of water crystallizes out progres- 

 sively with fall of temperature until the eutectic concentration 

 is reached at — 22°C. 



As pointed out above, sodium chloride must be carried by 

 the winds in appreciable quantities to the snowlields of glaciers. 

 In the change from snow to granular neve a process akin to 



