38 S EXPEDITION TOWARD THE NORTH POLE. 



be indicated more distiuctly by layers of sand and dust tlian in those of 

 the Alps by the dirt bands. Observations concerning the amount of 

 waste of the glaciers by evaporation or melting, or what I have called 

 ablation of the surface during a given time in different parts of the year, 

 would also be of great interest as bearing upon the hygrometric con- 

 dition of the atmosphere. A pole sunk sufficiently deep into the ice to 

 withstand the effects of the wind could be used as a meter. But it 

 ought to be sunk so deep that it will serve for a period of many months, 

 and rise high enough not to be buried by a snow-storm. It should also 

 be ascertained, if i^ossible, whether water oozes from below the glacier, 

 or, in other words, whether the glacier is frozen to the ground or sepa- 

 rated from it by a sheet of water. If practicable, a line of poles should 

 be set out with reference to a rocky peak or any bare surface of rock, in 

 order to determine the motion of the ice. It is a matter of deep interest 

 with reference to questions connected with the former greater extension 

 of glaciers, to know in what manner flat sheets of ice move on even 

 ground, exhibiting no marked slope. It may be possible to ascertain, 

 after a certain time, by the change of position of j)oles sunk in the ice, 

 whether the motion follows the inequalities of the surface, or is deter- 

 mined by the lay of the land and the exposure of the ice to the atmos- 

 pheric agents, heat, moisture, wind, «S:c. It would be of great interest 

 to ascertain whether there is any motion during the winter season, or 

 whether motion takes place only during the period when water may 

 trickle through the ice. The polished surfaces in the immediate vicinity 

 of glacier ice exhibit such legible signs of the direction in which the 

 ice moves, that wherever ledges of rocks are exposed the scratches and 

 furrows upon their surface may serve as a sure register of its progress; 

 but before taking this as evidence, it should, if possible, be ascertained 

 that such surfaces actually belong to the area over which the adjoining 

 ice moves during its expansion, leaving them bare in its retreat. 



The geological agency of glaciers will no doubt receive additional 

 evidence from a careful examination of this point in the Arctic regions. 

 A moving sheet of ice, stretching over a rocky surface, leaves such un- 

 mistakable marks of its passage that rocky surfaces which have once 

 been ylaciatcd, if I may thus express the peculiar action of ice upon 

 rocks, viz, the planing, polishing, scratching, grooving, and furrowing 

 of their surfaces, can never be mistaken for anything else, and may 

 everywhere be recognized by a practiced eye. These marks, in connec- 

 tion with transported loose materials, drift, and bowlders, are unmis- 

 takable evidence of the great extension which glaciers once had. But 

 here it is important to discriminate between two sets of facts, Avhich 

 have generally been confounded. In the proximity of existing glaciers, 

 these marks and these materials have a direct relation to the present 

 sheet of ice near by. It is plain, for instance, that the polished surfaces 

 about the Grimsel, and the loose materials lying between the glacier of 

 the Aar and the Hospice, are the work of the glacier of the Aar when it 



