454 0. D. von Engeln — Studies on Ice Structure. 



ingly the pressure was raised to 750 lbs. per square inch. The 

 following night the temperature fell. to a minimum of — 4°F., 

 and no change was apparent in the cylinder or pressure the next 

 day. At four o'clock in the afternoon, air temperature 13°F., 

 the pressure was raised to 1400 lbs. per square inch, the upper 

 limit of the calibrated scale of the press. At this pressure the 

 cylinder was allowed to stand for 36 more hours, the air 

 temperature meanwhile rising to 20°F. Then the cylinder 

 was removed from the press. It had been under varying 

 pressures for some 94 hours at air temperatures ranging 

 between — 4°F. and 20°F. On gently heating the metal cylinder 

 it was found possible to slip the ice core out complete, indicating 

 that there had been no bulging or distortion of the metal. 

 (See fig. 2.) 



The compressed ice was found to be of crystal clearness and 

 homogeneous, showing no line of separation to mark the junc- 

 ture of the rough-hewn prism of pond ice and the water frozen 

 around it. The most striking result, however, was the fact that 

 the ice mass had oeen completely recrystallized. The original 

 pond ice core was inserted with principal axes parallel to the 

 pressure direction, the new crystals extended across the cylinder 

 with their principal (and longer) axes at right angles to the 

 pressure direction. On slow melting and evaporation in the 

 laboratory the individual crystals 1/16 to 3/16 inches in diam- 

 eter and averaging 3/4 inch to 1 inch in length were outlined 

 by grooves along their contact planes. A further singular phe- 

 nomenon was the extension of the crystals straight across the 

 cylinder instead of radially inwards as might have been expected 

 by analogy to the structure of cakes of can-frozen artificial ice. 

 The boundaries of the crystals were irregularly polygonal, an 

 occasional one nearly hexagonal, much like glacier grains in cross 

 section but differing from these in that the crystals of the cylin- 

 der were greatly elongated. (See figs. 3 and 4.) Under 

 crossed nicols a section cut across one of the crystals exhibited 

 parallel extinction, indicating that it comprised a single, uniform 

 individual. Others showed wavy extinction in section, sug- 

 gesting distortion, as is also true of glacier grains. In no case, 

 however, were any traces of brecciation apparent. The elon- 

 gated form and wedge-shaped terminations in the artificial crys- 

 tals may have owed their difference from the glacier grains to 

 the fact that the conditions of our experiment permitted of no 

 movement in the ice mass involved. 



In a later experiment this last deduction was in a sense veri- 

 fied. An annealed, softer, copper cylinder was filled with ice 

 fragments of pond ice, glacier ice and snow in layers, and made 

 solid by filling up the spaces with water and freezing. Pres- 



