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the surface in the form of a spring. Perhaps this spring is one of 

 those clear cold pools with the water bul)bling up through its sanely 

 bottom from which w^e love to drink on a hot sunnners day ; or 

 again it is a swampy spot on the hillside where the cat-tails grow\ 

 In whatever form it issues from the ground, a tiny rill carries away 

 its overflow and this sooner or later joins the brook. 



The brook we see is simply tiie collected rainfall from the hill- 

 sides flowing away to join the river. It grows larger as other brooks 

 join it and becomes a creek and Anally a river. But where is the 

 dividing line between brook, creek and river? So gradually does 

 the brook increase in volume that it would be difficult to draw any 

 dividing line between it and the larger streams. And so with the 

 rills that formed the brook ; each is a part of the river, and the 

 names rill, brook, creek and river are merely relative terms. If we 

 go to other States, we should And that in different parts of the coun- 

 try brooks vary much in size. 



Brooks are but small-scale rivers ; and if we study the w^ork that 

 a brook is doing we shall find it engaged in cutting down or build- 

 ing up just as the river does, although, owing to the smaller size of 

 the brook, w^e can see most of these operations in a short distance. 

 Let us take our way through the wet grass and dripping trees to 

 the brookside and see what w^ork it is doing. 



The countless rain-born rills are pouring their muddy water into 

 tlie brook and to-day its volume is much greater than when it is fed 

 by the slower-moving underground w^ater of the springs, as it is in 

 fair weather. It roars along with its waters no longer clear but 

 full of clay and sand (" mud " as we call it). 



If we should dip up a glassful of this muddy water we should find 



that when it had settled, there remained on the bottom ot tiie giass a 



thin deposit of sediment. The amount of this sediment is small, no 



doubt, for a single glassful, but when we think of the great quantity 



of water constantly flowing by we can see that considerable sediment 



is going along with it. But this sediment in suspension is not all the 



load that the brook is moving. If you will roll up your sleeve, 



plunge your hand to the bottom of the brook and hold it there quietly, 



you will feel the coarser gravel and small stones rolling along the 



bottom. 



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