64 OUR NATIONAL PARKS 



and pines in Yosemite Valley shaken by an earth- 

 quake, their tops swishing back and forth, and 

 every branch and needle shuddering as if in dis- 

 tress like the frightened screaming birds. One 

 may imagine the trembling, rocking, tumultuous 

 waving of those ancient Yellowstone woods, and 

 the terror of their inhabitants when the first 

 foreboding shocks were felt, the sky grew dark, 

 and rock-laden floods began to roar. But though 

 they were close pressed and buried, cut off from 

 sun and wind, all their happy leaf-fluttering and 

 waving done, other currents coursed through 

 them, fondling and thrilling every fibre, and 

 beautiful wood was replaced by beautiful stone. 

 Now their rocky sepulchres are partly open, and 

 show forth the natural beauty of death. 



After the forest times and fire times had 

 passed away, and the volcanic furnaces were 

 banked and held in abeyance, another great 

 change occurred. The glacial winter came on. 

 The sky was again darkened, not with dust and 

 ashes, but with snow which fell in glorious abun- 

 dance, piling deeper, deeper, slipping from the 

 overladen heights in booming avalanches, com- 

 pacting into glaciers, that flowed over all the 

 landscape, wiping off forests, grinding, sculptur- 

 ing, fashioning the comparatively featureless 

 lava beds into the beautiful rhythm of hill and 

 dale and ranges of mountains we behold to-day ; 

 forming basins for lakes, channels for streams, 



