26 GLETSCH 



willow-herb {Epilobium Fleischert) was growing abun- 

 dantly in tufts among the pebbles, and many other Alpine 

 plants greeted our eyes. The heat of the sun was that 

 of midsummer, whilst a delicate air of icy freshness 

 diffused itself from the great frozen mass in front of us. 



Some large blocks of the glacer ice had fallen from 

 above, and lay conveniently for examination. Whilst the 

 walls of the ice-caves which have been cut into this and 

 other glaciers present a perfectly smooth, continuous 

 surface of clear ice, these fragments which had fallen 

 from the surface exposed to the heat of the sun were, as 

 seen in the mass, white and opaque. When a stick was 

 thrust into the mass, it broke into many-sided lumps of 

 the size of a tennis-ball, which separated, and fell apart 

 in a heap, like assorted coals thrown from a scuttle, 

 though white instead o^Nblack. These were the curious 

 glacier nodules, " grains du glacier," or " Gletcherkorne," 

 characteristic of glacier ice as contrasted with lake ice. 

 This structure of the glacier ice is peculiar to it, and is 

 only made evident where the sun's rays penetrate it and 

 melt the less pure ice which holds together the crystalline 

 nodules. According to Dr. J. Young Buchanan, these 

 nodules are masses of ice crystals comparatively free 

 from mineral matter, whilst the water around them, which 

 freezes less readily, contains mineral impurities in solution. 

 The presence of saline matter in solution lowers, in pro- 

 portion to its amount, the freezing-point of water. 

 Accordingly, although frozen into one solid mass with the 

 nodules, the cementing ice melts under the heat of the 

 penetrating rays of the sun sooner — ^^that is, at a lower 

 temperature — than do the purer crystalline nodules, and 

 allows them to separate. It is owing to this that the 

 exposed surface of glacier ice is white and powdery, 

 disintegrated by the superficial heat, and forming a rough 

 surface, on which one can safely walk. Lake ice does not 



