VALLEYS, PLAIN8, AND LOWLANDS 



237 



peal are terrific ; the roll from side to side is 

 repeated again and again, until at last it dies 

 off up the gulch in a muttering rumble that 

 shakes the whole atmospheric envelope. It 

 is only an accidental affair, and as soon as 

 the storm has passed, the valley once more ad- 

 dresses itself to sleep. The mountain-shadows 

 lie clear and cool along the ascending slopes, 

 and as the valley drowses the day through, these 

 shadows grow longer, each one stealing silently 

 down the western side, crossing the valley- 

 brook, and creeping up the far eastern slopes 

 as the sun sinks down beyond the mountain- 

 peaks. 



And what masses of shadow there are in a 

 valley ! However it may lie as regards the 

 points of the compass it is always sure to have 

 its slopes, its hills, and its mounds that cut 

 off the sun's rays and create the dark-green 

 patch. Even where the valley is quite wide, 

 the timber that usually grows thick in the 

 basin creates its own shadow in an almost im- 

 penetrable screen of foliage that shuts out the 

 sun. These forest shadows are usually dark, 

 moisture-laden masses, deep green in hue, and 

 seldom marked by brilliant colors. In fact, the 

 mountain-valley is not the place where nature 



