4:68 0. D. von Engeln — Studies on Ice Structure. 



Since the sea surface in the region (Yakutat Bay, Alaska) 

 where these observations were made is often quite completely 

 covered with floating ice, this temperature relation is not 

 impossible of attainment, — its existence was in fact confirmed 

 by thermometric observations by the writer in 1909. Incident- 

 ally, if the theory of the common ion does apply to the phe- 

 nomenon, as here suggested, the "'hammered silver" berg 

 surfaces afford a most striking and interesting natural example 

 of the action of a comparatively little known principle. 



The application of the experimental and other observations 

 considered above to the structure and flow of glaciers has con- 

 siderable significance. In the first place the position taken by 

 the late Professor Tarr, that experimentation with ice to have 

 a bearing on glacial phenomena must be done on ice aggregates 

 and not on single crystals, seems to be borne out by the evi- 

 dence indicating the presence of an interstitial film of saline solu- 

 tion between ice grains. The crushing strength tests on the 

 cubes indicate that at sufficiently low temperatures crevasses 

 may extend approximately 2000 feet deep from the surface 

 without closing by flow. Hence it is apparent why the upper 

 zones of glaciers seem quite brittle. 



The development of crevasses to the maximum depth of 

 2000 feet would, however, necessitate lower temperatures than 

 the evidence at hand shows to exist in the interior of glaciers. 

 Hess and Bliimcke* bored holes to a maximum depth of 153 

 meters in the Hintereisferner glacier. They found that the 

 temperature of the interior ice was only so much below the 

 melting point, under atmospheric pressure, as would be brought 

 about by the pressure of the superincumbent ice masses at any 

 given depth. Moreover, the temperatures at different depths 

 were very closely accordant with the calculated depression of 

 the melting point by a column of ice of that height. On the 

 other hand J. Vallotf observed a constant annual tempera- 

 ture of — 16'6° in the neve snow of the summit of Mont Blanc 

 at a depth of 10 to 13 meters below the surface. As the snow 

 from the highest parts of the neve field is that which eventu- 

 ally constitutes' the bottom layers of a valley glacier, and as 

 the deeper ice has progressively lower temperatures on account 

 of the pressure relations, it would appear that the bottom of a 

 glacier constitutes its coldest portion, also the thicker an ice 

 tongue the lower its interior temperatures may be. But the 

 factors that would need to be considered in an attempt to 

 deduce the body temperatures of an ice tongue of large size 

 are so various that a discussion of them would need to be long 



*Hess, H. : Die Gletscher, pp. 151-153 and pp. 319-320. Later 200 meters 

 depth was attained with same results. 



f Quoted by Hess, H.: Die Gletscher, p. 164. 



