1910.] INLAND-ICE OF THE ARCTIC REGIONS. 113 



suited in a warm wave which descended through the snow, following 

 the colder one, and so resulted in a maximum temperature not 

 immediately below the surface but at increasing distances from it 

 depending upon the duration of the warmer air temperatures at the 

 surface. Thus, a ten day foehn in January raised the temperature 

 at a depth of 2.2 meters, by a half a degree. It required over 

 two days for this rise in temperature to proceed to a depth of i 

 meter, and ten days for it to reach the depth of 2 meters. Similar 

 effects are produced with the coming of the more prolonged warm 

 weather of the summer season (see Fig. 33). 



When the surface zone of the snow has reached the fusing point 

 of snow, melting begins rapidly. Peary has drawn a graphic pic- 

 ture of the effect of the warm season upon the margins of the 

 Greenland ice. Late in the spring the warmth of the sun at midday 

 softens the surface first along the outermost borders of the ice, 

 and this, freezing at night, forms a light crust. Gradually this 

 crust extends up in the direction of the interior, and as the season 

 advances the surface of the marginal rim becomes saturated, with 

 water. This zone of slush follows behind the crust towards the 

 interior in a continually widening zone as the summer advances. 

 Within the outermost zone the ice is so decomposed that pools come 

 to occupy depressions upon the surface and streams cut deep gullies 

 into the ice. At the same time the ice shows a more dirty appearance 

 through the concentration of the rock debris due to the melting 

 of its surface layers. By the end of the season, pebbles, boulders 

 and moraines have in places made their appearance on the surface, 

 and the streams have left a surface of almost impassable roughness.^" 



Differential Surface Melting of the Ice. — In his ascent of the 

 western margin of the ice near the latitude of Disco Bay, Peary 

 encountered lakes surrounded by morasses of water saturated with 

 snow. The ice within this zone is crevassed, and down the fissures 

 some of the surface streams disappear, at times in a large water-fall, 

 and again in a " mill " of its own shaping. Baron Nordenskiold 



*'E. von Drygalski, " Gronland-Expedition," /. c, pp. 460-466. 

 ^ Peary, Geogr. Jour., 1. c, p. 218. See also Nordenskiold, " Gronland ''" 

 (German ed.), pp. 125-138. 



PROC. AMER. PHIL. SOC., XLIX, I94 H, PRINTED JUNE 9, I9IO. 



