0. D. von Engeln — Studies on Ice Structure. 457 



originally glacier ice was coarsest, the crushed top ice finest, 

 but all parts showed the same granular structure, but not elon- 

 gated crystals, and the grains were also variously oriented 

 crystallographically. The appearance of this cylinder is shown 

 in fig. 6. 



As the ice of this cylinder had a complicated history the 

 experiment was repeated with an annealed cylinder filled with 

 cracked pond ice. and snow only, no water frozen in. This 

 was compacted with pressures up to 1400 lbs. per square inch 

 with much swelling of the cylinder. Then the plunger was 

 removed and more filling of snow and cracked ice put in. 

 This experiment was carried on for about 5 full days, air tem- 

 peratures meanwhile ranging between 5° and 27° F. On 

 removal from the cylinder the cracked ice layers were found to 

 be clear and glassy, the snow layers glassy but clouded with 

 innumerable air bubbles ; the whole was a homogeneous ice 

 mass. On melting down the characteristic, granular structure, 

 obtained in previous experiments, was found to have developed 

 in this also in all parts, but the grains were larger in the layers 

 of cracked ice. Under crossed nicols extinction was found 

 to be uniform within a given grain boundary. Similar results 

 were obtained on compressing snow alone. 



It seems from these experiments that a granular ice can be 

 developed from snow by pressure with accompanying move- 

 ment at air temperatures eliminating the possibility of pressure 

 melting and regelation. The pressures required to bring about 

 flow and change of structure are also interesting, in that they 

 correlate so nearly with the yield point pressures obtained in 

 the unsupported cube experiments. It is to be remembered, 

 however, that the pressure figures for most of the metal cylin- 

 der experiments are by no means exact, inasmuch as the area to 

 which pressure was applied must have been constantly changing 

 as the cylinder swelled, and can hardly have been transmitted 

 uniformly per unit of area throughout the mass during the 

 progress of the experiment. 



In the second type of the compression experiments with 

 metal cylinders it was planned to test the possibility of free 

 and continuous flow of ice at temperatures sufficiently low 

 to eliminate the development of pressure melting and regela- 

 tion. A heavy iron cylinder bored out to 2 5/16 inches diam- 

 eter, with a lateral orifice 3/4 inch in diameter, near the solid 

 base was used. A solid steel plunger was turned to fit very 

 accurately into the larger opening of the cylinder. It was pro- 

 posed to force ice placed in the cylinder through the lateral 

 orifice by applying pressure by means of the steel plunger. 

 The arrangement of the experiment is clearly shown in fig. 1. 



On March 5th at an air temperature of 22° F. the cylinder 



