250 OUR NATIONAL PARKS 



middle region, as stated above, rarely exceeds 

 ten feet. Evaporation never wholly ceases, even 

 in the coldest weather, and the sunshine between 

 storms melts the surface more or less. Waste 

 from melting also goes on at the bottom from 

 summer heat stored in the rocks, as is shown by 

 the rise of the streams after the first general 

 storm, and their steady sustained flow all winter. 

 In the deep sugar-pine and silver-fir woods, up 

 to a height of eight thousand feet, most of the 

 snow lies where it falls, in one smooth universal 

 fountain, until set free in the streams. But in the 

 lighter forests of the two-leaved pine, and on the 

 bleak slopes above the timber line, there is much 

 wild drifting during storms accompanied by high 

 winds, and for a day or two after they have 

 fallen, when the temperature is low, and the snow 

 dry and dusty. Then the trees, bending in the 

 darkening blast, roar like feeding lions ; the 

 frozen lakes are buried ; so also are the streams, 

 which now flow in dark tunnels, as if another 

 glacial period had come. On high ridges, where 

 the winds have a free sweep, magnificent over- 

 curling cornices are formed, which, with the ava- 

 lanche piles, last as fountains almost all summer ; 

 and when an exceptionally high wind is blowing 

 from the north, the snow, rolled, drifted, and 

 ground to dust, is driven up the converging 

 northern slopes of the peaks and sent flying for 

 miles in the form of bright wavering banners, 



