232 



THE BROOK BOOK 



straight, though it was likely to be narrow. When 

 the water came to a very steep slope, it went 

 faster and faster. If, at the foot of the slope, 

 there happened to be a perpendicular ledge, the 

 water leaped through the air and reached the 

 ground below, only to seek out again the steepest 

 path down the next hill and to speed on its way." 



"That explains the brook itself," I said, "and 

 the waterfalls and the rapids. But the gorges?" 



"Not so fast! It has taken those brooks some 

 thirty thousand years to make the gorges, although 

 they are comparatively modern institutions, geo- 

 logically speaking." 



I was fairly stunned by the thought that any- 

 thing could be so ancient. Brooks seem to have 

 such a youthful way with them, too. I was ready 

 to listen in silence and let the Geologist take his 

 time. 



"As the water continued on its way down hill," 

 he went on, "seeking ever the lowest level, it 

 grew in volume with every rain and every drop 

 of melted glacier. Moving along over the hills 

 and valleys, the glacier had gathered much rub- 

 'bish; stones, gravel, etc. These it gave up as it 

 melted and the brook received many of them. 

 Whenever the stream had to pass over a nearly 

 level area, it was impossible to carry all this bur- 

 den further. So some of the stones were left 

 behind on the flat places. Some of the smaller 

 ones and the gravel and sand went on with the 

 brook. These stones had sharp edges where they 

 had been broken by the glacier. As the brook 



