156 I. C. Russell — Expedition to Mount St. Elias. 



awakened by another roar. To witness such a scene under the 

 most favorable conditions was worth all the privations and 

 anxiety it cost. 



Besides the streams of new snow, there were occasional ava- 

 lanches of a different character, caused by the breaking away of 

 portions of the cliffs of old snow, accumulated, perhaps, during 

 several winters. These start from the summits of precipices, 

 and are caused by the slow downward creep of the snow-fields 

 above. The snow-cliffs are always crevassed and broken in 

 much the same manner as are the ends of glaciers which enter 

 the sea, and occasionally large masses, containing thousands of 

 cubic yards, break aAvay and are precipitated down the slopes 

 with a suddenness that is always startling. Usually the first 

 announcement of these avalanches is a rej)ort like that of a can- 

 non, followed by a rumbling roar as the descending mass ploughs 

 its way along. The avalanches formed by old snoAV are quite 

 different from those caused by the descent of the new surface 

 snow, but are frequently accompanied by surface streams in case 

 there has been a recent storm. The paths ploughed out by the 

 avalanches are frequently sheathed with glassy ice, formed by the 

 freezing of water produced by the melting of snow on account of 

 the heat produced by the friction of the moving mass. A third 

 variety of avalanches, due to falling stones, has already been 

 noticed. 



The floor of my snow-chamber was the surface of the old snow 

 on which we had pitched our tents at the time we first reached 

 that camping place. On this hard surface, and forming the walls 

 of the cell, there 'were thirty inches of clear white snow, the 

 upper limit of which was marked by a blue layer of ice about a 

 quarter of an inch thick. This indicated the thickness of snow 

 that fell during the first storm. Its surface had been melted and 

 softened during the days of sunshine that followed its fall, and 

 had frozen into clear ice. Above the blue band which encircled 

 the ujoper portion of my chamber was the soft, pure white snow 

 of the second storm. The stratification of snow which I had 

 seen fall rendered it evident that my interpretation of the strat- 

 ification observed in the sides of crevasses was correct. The 

 snow when it fell was soft and white, and composed of very 

 fine crystals ; but under the influence of the air and sunshine it 

 changed its texture and became icy and granular, and then re- 

 sembled the neve snow so common in high mountains. 



