A MOUNTAIN STREAM 153 



But what we see in this flat stretch is like a silver 

 serpent with a long sinuous body. There are several 

 places where a bend has turned back on the main 

 course and almost touched another higher up. If it 

 did this there would be a grassy island formed. We 

 see that the stream eats into the back on its deeper, 

 swifter side and deposits sand on its shallower, slower 

 side. This goes on until it meets some obstacle on 

 the deeper side or until the falling in of a stretch of 

 bank deflects the course, and the eating in commences 

 on the other side. So year by year the winding stream 

 shifts its course through the meadow. 



We suppose that the line of the stream was very 

 long ago a lint of weakness in the earth's crust a 

 crack, in short ; kit, given a beginning, we can under- 

 stand from the tehaviour of the stream to-day how 

 the bed has been leepened and a beautiful gorge cut 

 back into the hill. What do we see ? 



Here are the Fa^ls of Niagara in miniature. We 

 see that the rock a\ the foot of the waterfall is of 

 softer material than\hat above. It gets eaten away 

 more rapidly just becfyse it is softer, but there is also 

 the wear and tear ofVhe shifting stones which the 

 whirling water uses as\pols. Just as one can get in 

 behind the tremendousVurtain of falling water at 

 Niagara, so here one ca^see that a miniature cave is 

 being carved out behind W cascade. Some day this 

 will have been eaten in so W that the roof falls in and 

 a big slice breaks off from tV undermined harder rock 

 above. The top of the fal is shifted back a little, 

 nearer to the hills. The fllen rock, broken into 

 pieces, supplies materials fo\ new tools for more 

 sapping and mining. What taV s place at a waterfall 



